The present invention provides a hull detection underwater robot that comprises an underwater robot body which is equipped with an environment sensing device, a movement sensing device and a movement executing device. The environment sensing device comprises an ultrasonic thickness gauge, image sonar and an underwater low light level camera. The movement sensing device comprises an optical fiber compass and a depth gauge. The movement executing device comprises a conduit propeller and a three degree of freedom tripod head. All devices are connected with a PC/104 computer in a hyperbaric chamber of the underwater robot body. A control program is embedded in the PC/104 computer. The PC/104 computer collects the information of the environment sending device and the movement sensing device, then communicated with a water surface main control computer for the large data volume network communication of mixed data and outputs a control instruction of the water surface main control computer to the propeller.