Abstract: Inverse beam forming (IBF) has higher azimuth resolution and array gain than conventional beam forming. It can effectively suppress noise, but has higher side lobe levels. Therefore IBF uses the statistical information of peak values as its output. This method resolves the problem of signal detection with high side lobe levels, but loses information of the power spectrum density. In this paper, by analyzing the cause of high side lobe in inverse beam forming, a moving average method is used to suppress side lobes. Simulation shows the effectiveness of side lobe suppression with the first side lobe reduced by 2~3 dB, and high azimuth resolution. The conventional method can be used to export results and reserve informa-tion of power spectrum density. Merits of the moving average method are verified in the processing of experimental data acquired at the sea.