Abstract: An underwater multi-channel NAH system has been developed and used for NAH experiment presented in this paper. Difficulties concurring the calibration of the system and design of the frame of the hydrophone line array for much less scattering are solved. The NAH experiment for a large area planar transmitting array is carried out in an anechoic water tank. The distributions of pressure intensity on the surface of the source are given through data processing. The radiated acoustic power of the transmitting array as a whole and each element of it are calculated respectively. The far field beam pattern and directional parameters are also deduced. The experimental results demonstrate that the use of pulse signal in NAH, the sequential scattering and composition method for data acquisition from the line array is feasible. The design of system and method of test are applicable to large-scale NAH systems.