Abstract: Experiments on a mainlobe constrained adaptive array processor is presented. In order to verify the mainlobe constraint and the jammer cancelling Performance about the adaptive array, an experimental system based on a hydrophone array and TMS320C25 digital signal processor is constructed togather with an adaptive spatial prefilter as reguired by previous theoretical analysis. Some typical experimental results are given. The experiments are carried out both in water pool and on the sea. The effects of the input signal-to-noise ratio (SNR), Signal-to-jammer ratio (SJR), signal and jammer bandwidth. and the adaptive step size on the system Performance are studied in detail. The results show that the theoretacal analysis is correct