Abstract: Three typical Al-Si bimetal driving membrane structures are analyzed in this paper. The deflection of the three structures is calculated by two-dimensional finite element models using the finite element method (FEM) software SAP91. The results show that the deflection direction, maximum center deflection of the membrane and the effective change of the volume all rely on the structure parameters. Different deflection direction can be obtained through the different structure design. If the structure parameters are optimized, the characteristics of the membrane can be improved dramatically.