Abstract: The control of the mini underwater robot with PID algorithm based on the graphic computer language (G language) is presented . The course and depth of the underwater robot is controlled by the PID algorithm so that its stability ean be enhaneed. The experiment indieates that the robot can observe the object exactly by locking its course. On the other hand, the depth of the robot is also controlled by PID algorithm so that it can work at given depth steadily. Thereby, the performanee of the robot will be improved by this controlled method and it can work at some complex circumstances.