Aimed at the low frequency of traditional ultrasonic transducers in low frequency domain,a new theoretical model of microbridge was designed,with analysis and research of the mechanical behavior. Solid modeling,modal analysis and electrostatic analysis were carried out with COMSOL 5. 4 for the silicon-based microbridges of the antiferroelectric thick film,which can produce the effect of phase-transition induced strain. Applied with the orthogonal design,the reasonable structure sizes of the microbridge component with small stress and large frequency were obtained. They can provide an important basis for the following fabrication. When the microbridge is 800 μm（ L） × 100 μm（ W）,the corresponding stress is 0. 352 GPa and the resonant frequency equals to 115. 19 kHz,which is superior to traditional ultrasonic transducers in the aspect of better performance based on the smaller sizes.