To address the trajectory deviation of remotely operated vehicles （ROVs） during operations in complex environments-caused by the nonlinear towing of a negative-buoyancy umbilical cable and the transient impact of ocean waves-the dynamic response of the umbilical cable and an anti-disturbance trajectory tracking control method are investigated. First， a dynamic model of the umbilical cable is established using the lumped-mass method and the Morison equation， and the time-varying tension and towing-disturbance characteristics under typical operating conditions are analyzed with the OrcaFlex software. Second， an improved line-of-sight （ILOS） guidance law is designed to achieve dimensionality reduction， decoupling， and guidance of the three-dimensional trajectory； a linear extended state observer （LESO） is introduced to perform real-time estimation and feedforward compensation of the unknown composite disturbances arising from cable towing forces and the wave-current field， and a power-rate sliding mode control （PRSMC） is combined to smooth the control output and suppress high-frequency chattering. Finally， a co-simulation platform based on MATLAB and OrcaFlex is built for closed-loop verification. Simulation results show that， in tracking a complex polyline trajectory， the proposed control method reduces the mean absolute errors （MAEs） of the three degrees of freedom by 28.40%， 27.95%， and 49.78%， respectively， compared with conventional sliding mode control （SMC）.The results indicate that， under complex trajectories and multi-source composite disturbances， the proposed control algorithm can accurately observe and compensate in real time for the unknown current-cable coupled disturbances， effectively reducing steady-state error and system chattering， and achieving good tracking accuracy and strong robustness. This study can provide a reference for the design and application of anti-disturbance control systems for ROVs in strongly disturbed environments.