In order to precisely control move of underwater robots, the fuzzy PID dual-mode controller based on fuzzy rules switching is invented, combining the conventional fuzzy controller and the more precise PID controller. Fuzzy rules are switched on the basis of different moves of underwater robots. The new controller has been conducted simulation and field experiments on underwater synthetic explored robots. The experiments show that, with pragmatic design and good dynamic performance like traditional controllers, the new controller improves precision while reduces overshoot. It also has good robustness when dealing with uncertainty of the model and external disturbances. On the whole, it has higher pragmatic value.