Abstract: Objectives Surf-riding/broaching poses a significant threat to the navigation safety of high-speed vessels. Therefore, this study investigates the surf-riding phenomenon in both waterjet-propelled and propeller-driven ships, aiming to reveal how different propulsion systems influence the occurrence of surf-riding. Methods A surf-riding motion equation was established for both waterjet-propelled and propeller-driven vessels. By integrating vulnerability criteria assessment with time-domain simulations, this study comparatively analyzed the motion characteristics and force variation processes during surf-riding under different propulsion systems, elucidating how distinct propulsor mechanical properties influence the occurrence of surf-riding. Results The simulation results demonstrate significant differences in thrust variation characteristics between waterjet and propeller systems. Due to the waterjet's insensitivity to speed changes, waterjet-propelled vessels exhibit a higher probability of surf-riding occurrence compared to propeller-driven ships. Conclusions The mechanical analysis elucidates the fundamental mechanism underlying the differential surf-riding characteristics between waterjet and propeller propulsion systems. These findings provide valuable references for propulsion system selection in ship conceptual design.