Ocean bottom seismometer (OBS) is a major means of natural earthquake observation in marine. The noise recorded by the instrument is divided into environmental noise and instrument noise. Using the data collected by the Wuyu Island Submarine Seismic Observatory from September 3,2018 to July 1,2019,we analyzed the instrument self-noise of the strong seismic OBS and the broadband OBS in the sea environment. Two channel cross-correlation model is used to calculate the power spectrum by windowed average periodogram method,and then 1/3 octave integral is used as smoothing processing. Finally,the self noise power spectrum density of the instrument is obtained. By comparing and analyzing the power spectrum of self-noise of the same type of instrument,we found that the variation trend of self-noise of the same instrument is the same,but the size of self-noise is different,and the difference also exists for different instruments and different components of the same instrument.