Target tracking system is widely used in mobile surveillance cameras and intelligent transportation systems. Robots equipped with target tracking system work in various fields. According to the field conditions, such as in the water or in the air, the weight of the robot is limited. In addition, the radio wave attenuation of underwater robots in the water is significant. Therefore, laser is being used to replace radio wave The research of mobile communication. The master and slave of the robot are equipped with transmitter and receiver to irradiate laser to each other's receiver for communication. In the case of underwater robot, the receiver and transmitter need to follow each other's direction even when the underwater robot is moving.