Thermal deformation is the main reason for the change of accelerometer output with the temperature. Based on analysis of the working principle of capacitive accelerometer, finite element method was applied in the simulation of thermal deformation. Calculation results indicated that when the sensor structure is symmetrical completely, the differential configuration can cancel the thermal deformation and there is no drift for the output of accelerometer; when nonsymmetry occurs by machine error, the thermal deformation will develops towards the direction of less strength, and the temperature drift occurs. The temperature drift experiment indicated that when temperature increasing 40 益 , the output of accelerometer decreases 76 mV. It was suggested that capacitive accelerometer should be manufactured accurately to reduce thermal deformation of sensor structure.