A hexagon ultrasonic transducer array based on MEMS is presented in this paper.According to the radiation sound field of square piston,the sound pressure intensity and directivity formula of individual array element has been calculated using Rayleigh integration.The amplitude distribution of array has been plotted out by numerical method based on Huygens′s principle.Several factors such as element size,spacing and number that affect the wave width,sharpness angle and sidelobe level are analyzed theoretically.The results show that the proposed hexagon array not only can eliminate the grating lobe,suppress side lobe and reduce the major beam width,but also has a very intensive directivity at low frequency (~10 kHz).The optimization of array parameters can provide guidance for array design and sound field distribution analysis.