Abstract: In order to comprehensively improve marine seismic study and monitoring capability, ocean bottomseismograph (OBS) was developed. This paper describes the basic working principle of OBS, proposes its performance specifications. The overall design, composition and structure principle of the various components of developed broadband OBS are described in detail. This paper also introduces application example in the South China Sea, and shows the seismic waveforms from earthquakes recorded by the broadband OBS on the sea floor at 3000 m depth.