Robots that operate underwater (underwater robots) replace humans in searching for victims, weapons, and evidence in criminal cases… Normally, robots move underwater thanks to the Human control from a shore station, however, when detecting a suspected object as a search target, the robot needs to stabilize in one position to observe and salvage the object. The level of position stability and working posture of the robot greatly affects the quality of observed images and the ability to salvage objects. Therefore, the topic group chose history Use a gravity-compensated PID automatic controller to perform the above task, because this is a set The controller has a fast response time, suitable for the object of the problem. Simulation results on Matlab/Simulink show that the robot is quite stable at the reference position. Result Actual testing has proven the correctness of the simulation and meets the requirements of the problem.