Abstract: With the increasingly stringent global demands for energy conservation, emission reduction, and underwater radiated noise (URN) control in the maritime industry, conventional marine propellers have encountered an insurmountable performance bottleneck to further enhance propulsive efficiency and mitigating underwater noise. The fundamental limitations of traditional propellers stem from the inevitable tip vortex formation at the blade tips, which easily induces cavitation, intense vibration, and high levels of radiated noise, while their cantilever beam-like structural design also leads to poor structural rigidity and hydroelastic issues. As a novel underwater propulsion technology, the toroidal propeller has demonstrated considerable potential for cavitation suppression, noise reduction, and hydrodynamic performance improvement by virtue of its distinctive closed-loop blade topological structure, making it a promising alternative to conventional propellers for meeting the modern shipping industry's stringent requirements. This paper aims to systematically review the research status of marine toroidal propellers, comprehensively analyze their structural characteristics, hydrodynamic and acoustic properties, and deeply discuss the latest research progress and practical application status in both domestic and international contexts, while also identifying and analyzing the key technical challenges faced in the industrialization of this technology. To achieve the research objectives, the study first elaborates on the unique geometric configuration and structural features of toroidal propellers, including their closed-loop blade structure, segmented blade system with forward and aft sections, and innovative toroidal connection design, and summarizes the established parametric modeling methods for their complex 3D geometric shapes. Then, the paper conducts an in-depth review of existing research on the hydrodynamic performance of toroidal propellers, involving numerical simulations based on RANS, LES and DES methods, as well as experimental studies including model tests and full-scale ship trials, and quantitatively compares the performance differences between toroidal propellers and conventional propellers in terms of thrust coefficient, propulsive efficiency and advance coefficient adaptability. In addition, the cavitation suppression mechanism and acoustic characteristics of toroidal propellers are analyzed, with a focus on the research results of tip vortex evolution, cavitation inception and development, and underwater radiated noise reduction effect. The research also sorts out the current application status of toroidal propellers in small unmanned boats, recreational vessels and experimental platforms, and compares the different development models of toroidal propeller technology between international enterprises and domestic universities and research institutions. The results show that the toroidal propeller's closed-loop blade structure fundamentally eliminates the free blade tip of traditional propellers, effectively suppressing the shedding of tip vortices and raising the cavitation inception threshold, thus reducing high-frequency tonal noise significantly; in medium and low speed, high slip conditions, its propulsive efficiency is significantly higher than that of conventional propellers. However, the performance gain of toroidal propellers shows significant discreteness in different studies, and their efficiency is lower than that of traditional propellers in high-speed cruising conditions due to the increased wetted surface area and friction resistance. In terms of acoustic performance, toroidal propellers can reduce the overall sound pressure level by 4-6 dB in the axial plane and 2-14 dB at the blade passing frequency and its higher harmonics, but there is a potential risk of low-frequency flow-induced noise caused by complex flow separation in the toroidal channel. The paper also finds that international research on toroidal propellers has entered the engineering exploration stage with commercial products on the market, while domestic research is still in the initial stage focusing on principle discussion and numerical simulation, with a large gap between theoretical research and practical application. It is concluded that the marine toroidal propeller has significant application potential in high-efficiency, low-cavitation and low-noise underwater propulsion due to its unique structural advantages, and it is expected to drive the innovation of underwater propulsion technology and play an important role in meeting the energy conservation, emission reduction and vibration and noise reduction requirements of the modern maritime industry. However, the industrialization and large-scale application of toroidal propellers are currently restricted by multiple key technical challenges, including unclear vortex evolution mechanism, inaccurate scale effect correction, complex intelligent multidisciplinary design, high manufacturing cost caused by sophisticated 3D geometric structure, and the lack of unified performance evaluation standards and system integration test specifications. Despite the existing gap between theoretical research and practical application, with the continuous advancement of numerical simulation technology, the iteration of intelligent optimization algorithms, the development of advanced manufacturing processes and materials, and the establishment of a sound engineering application standard system, the technical bottlenecks of toroidal propellers are expected to be gradually resolved. Future research should focus on the in-depth study of the fluid dynamics mechanism of toroidal propellers, the construction of intelligent multidisciplinary design and optimization systems, the breakthrough of high-precision and low-cost manufacturing processes, and the formulation of unified test and evaluation standards, so as to accelerate the standardization and industrialization process of toroidal propellers and realize their engineering application in more marine vessel types.