Abstract: In the capacitance diaphragm gauge,the pressure-sensitive diaphragm usually needs to be pretensioned before installation,and then fixed.In order to study the effect of pressure-sensitive diaphragm pretension on the output characteristics of the capacitance diaphragm gauge,taking existing capacitance diaphragm gauges as object,a finite element model is established based on the COMSOL Multiphysics software,and the simulation solutions of the output capacitance under different pretensions are obtained,and compared with the theoretical calculation results,and the effect of the pretension on the output capacitance is analyzed.At the same time,the variation regularity of linearity and sensitivity of capacitance diaphragm gauge with pretension are analyzed,and the strength of the pressure-sensitive diaphragm under the maximum load is checked.The results show that the pretension has a significant effect on the output characteristics of the capacitance diaphragm gauge.The output capacitance decreases with the increase of the pretension,the theoretical calculation value of output capacitance is basically consistent with the simulation value.The greater the pretension,the better the linearity of the capacitance diaphragm gauge,but the lower the sensitivity.When the pressure-sensitive diaphragm pretension is 50MPa,the linearity of capacitance diaphragm gauge is 7.3%,the sensitivity is 0.043 3 pF/Pa,after the circuit compensation,the better linearity and sensitivity can be obtained.The stress of the pressure-sensitive diaphragm under the maximum load is 95.5 MPa,which can meet the working requirements.