Abstract: The output result of capacitance diaphragm gauge with singular-capacity structure is often adversely affected by the working environment. A dual-capacity structure is designed to improve this situation. In order to study the influence of dual-capacity structure on the capacitance output characteristics of capacitance diaphragm gauge, a finite element model of the dual-capacity structure is constructed based on COMSOL Multiphysics software according to capacitance calculation theory and FEA(Finite Element Analysis). Through theoretical calculation and software simulation, the theoretical and simulated values of measured capacitance and reference capacitance under different load conditions are obtained, and the variation of capacitance of different structures with load is analyzed. The results show that the dual-capacity structure can optimize the capacitance output characteristics of capacitance diaphragm gauge. Compared with the singular-capacity structure, the features of the dual-capacity structure of capacitance diaphragm gauge are as follows: when the deflection of the pressure-sensitive diaphragm is less than its thickness, the linearity increases by 0.6% and the sensitivity reduces by 0.6 pF/Pa; When the deformation of the pressure-sensitive diaphragm is close to the fixed plate, the linearity increases by 3.6% and the sensitivity reduces by 0.001 pF/Pa.