摘要：A kind of piezoresistive ultrasonic sensor based on MEMS is proposed,which is composed of a membrane and two side beams.A simplified mathematical model has been established to analyze the mechanical properties of the *** the basis of the theoretical analysis,the structural size and layout location of the piezoresistors are determined by simulation *** boron-implanted piezoresistors located on membrane and side beams form a Wheatstone bridge to detect acoustic *** membrane-beam microstructure is fabricated integrally by MEMS manufacturing ***,this paper presents the experimental characterization of the ultrasonic sensor,validating the theoretical model used and the simulated *** sensitivity reaches -116.2 dB（0 dB reference = 1 V/μbar,31 kHz）,resonant frequency is 39.6 kHz,direction angle is 55°.