Abstract: [Objective]To solve the problem of partial failure of the actuator of underwater salvage robot caused by the decrease of shipborne power supply voltage or the corrosion of control system circuit. [Methods]Considering the influence of complex ocean conditions in deep-sea torpedo, cargo shipwreck and other engineering salvage operations, the terminal sliding mode observer is used to observe the uncertain disturbance of the system, and the fault-tolerant control method and finite-time control method are used to estimate the fault coefficient of actuator on-line, a finite-time trajectory tracking fault-tolerant control scheme with terminal sliding mode observer is designed. [Result]The system output of this scheme is smooth, stable and can reach the desired trajectory quickly. At the same time, compared with the traditional fault-tolerant control scheme, the steady-state time of the underwater salvage robot control system is reduced (the lateral displacement is reduced by 10s and the longitudinal displacement is reduced by 15s). [Conclusion]This study can provide theoretical reference for trajectory tracking of underwater construction machinery, and has practical engineering significance.