Abstract: Precise bearing and automatic tracking for target is an important thesis in passive sonar.An algorithm,which can precisely estimate the value of Direction Of Arrival (DOA) of the target is drived in this paper.The relationship between bearing accuracy and the array apeture and signal frequency band is expressed.The expression of time delay estimation and bearing accuracy is presented.The DOA of the target can be precisely calculated by using the parabolic interpolation in the neiboughood of main lobe of the directivity function,it is easy to implement the automatic tracking in real time.The system simulation shows that the algorithm derived in this paper has very good Performance and it is easy to realize in hardware.