In recent years, the exploration and utilisation of the environment has become in full swing with the advancement of technology. However, the environment has also suffered a certain degree of damage in the process. As a result of the increasingly serious environmental problems, various environmental issues have become hot spots in society. Among them, marine environmental problems have undoubtedly become one of the focuses of attention. Therefore, the robot design for underwater water quality detection has become an important issue. This paper will mainly focus on the design and research of the hardware circuit system of the underwater detection robot, and give the relevant design scheme. The underwater robot will achieve the following functions: floating suspension at a certain depth in the ocean; synchronously detecting the radiation intensity of x-rays and -rays underwater and transmitting the data to the ground to achieve real-time monitoring; maintaining the dynamic balance in the water. Therefore, this paper analyses the pressure sensor circuit, the inertial sensor circuit, the underwater x-ray and -ray detection probe circuit and the DC motor drive circuit, determines the interface relationship of each part, and at the same time, uses the Arduino mega 2560 as the control panel, and provide the appropriate voltage according to the needs of each circuit to achieve the hardware circuit design of the robot.