In terms of the pitch angle control of a remotely operated vehicle (ROV) in the complex underwater environment,a cascade PID controller was designed.The force situation of the underwater ROV was analyzed,and the kinematics model of the pitch control system of the ROV was established.The cascade PID controller has bigger adjusting range and faster response speed than traditional PID controllers,so it is more flexible when designing,and can deal with the problem produced by the practical nonlinear factors.The simulation results show that the cascade PID controller provided is of better control performance than traditional PID controllers for the pitch control of the ROV.The pool tests illustrate the feasibility of the cascade PID controller in the pitch angle control of the ROV.