Abstract: How to use the method of signal processing to accomplish the port/starboard discrimination on a single line array is a valuable research thesis, the paper use the array shape distortion during the towing of the line array to solve port/starboard discrimination problem on a single line array. First build two models of the possible distortion of the towed line array:the array is traffic circle like and the array is landscape oriented discreet error line-like array; and then analyze the problem brought to the towed line array beam forming by these two conditions; points out that the symmetric features of the line array principle is destroyed by the distortion array. According to the beam forming after distortion, this method can realize the port/starboard distinguishing of the target. With the proper standard error condition of hydrophones, the mirror source restrain ratio can be over 10dB, and can improve the beam forming greatly. Simulation research have proves for that above conclusion.