In the conventional beam-forming (CBF) under low signal to noise ratio (SNR)

the spectrum values of each azimuth are accumulated by equal weight

and the spectrum values of targets are usually inundated in those of non-targets

so the underwater targets with unknown radiated noise can be hardly detected.In order to detect the effective target signal

a target detection method based on the beam domain phase stability is proposed.According to the feature that the underwater target radiates noise with stable line spectrum and the difference of the beam domain phase stability of each azimuth

this method cumulates spectrum values of each azimuth based on the beam domain phase variance by weighted statistical algorithm.Therefore

the azimuth of the underwater target is effectively estimated.The numerical simulation and experimental results both verify that

compared with the conventional beam-forming

this method can well enhance the energy of the target azimuth

restrain the background noise disturbances of non-target azimuth

and improve the SNR gain of the target detection.