The ocean bottom seismometer is an important marine seismic observation equipment. In view of the characteristics of high noise of ocean currents and frequent human activities in China"s offshore shallow ocean, the chained seismic observation method is proposed and the mechanical structure of ocean bottom cabled seismometer node is designed. Firstly, the overall structure of node is designed according to the size and layout of the internal components. Then the shell thickness, end cover thickness and sealing size are determined by theoretical calculation and finite element simulation. Finally, the pressure test verifies that the pressure resistance and water tightness of the designed seismometer node structure meet the requirements, and the seismic observation comparison test verifies its ability to receive natural earthquakes. The ocean bottom cabled seismometer will be applied to the actual seismic observation in the offshore area of Zhejiang Province to provide real-time and continuous seismic observation data.