Based on radiant sound field expression for single rectangular piezoelectric wafer,this paper gives analysis the infection each factor causing to sound pressure intensity and directivity, concrete methods to minimize major lobe while narrowing side lobes is put forward. As an example, the paper derives superimposed sound field formula for 16 wafer phased array probe, analyzes relationship of superimposed sound pressure and distance between focus and transducer,simulates and discusses influence on the quality of synthetic sound beam of phased array probe by factors such as element number,distance of adjacent elements.Simulation result is considerably consistent to related theory,which provides reference for evaluation and measurement for sound distribution and production of high quality phased array probes.