Abstract: There are a lot of published studies which discuss the anti-interference problem in the noise background radiated by a towing ship based on the array with an interval of 1/2 wavelength between elements. Not the 1/2 wavelength interval one but the 1/4 wavelength interval one is to be concerned because of the obvious benefit to detecting signal in the noise background radiated by towing ship. Research shows that the end fire directivity of the array with an interval of 1/4 wavelength between elements is not symmetric, which can suppress tow-ship interference effectively. And, the combined sensors with null beam pattern are proposed as elements to form the 1/4 wavelength interval array, with which the detection ability in the tail direction can be improved more significantly.