This paper investigates the effects of environmental temperature fluctuations on the performance of a MEMS accelerometer. The model, vibration equation, and calculation of the output of detection capacitance for the accelerometer are presented. The fluctuations in temperature are considered when evaluating the actual performance of the device. The analysis results show that temperature fluctuations have a great influence on the output of the accelerometer although it has little influence on the resonant frequency of sensing mode and the sensitivity of detection capacitance. The performance deviations under the effects of temperature fluctuations are calculated accurately, which provides a reference for the design of temperature compensation method and robust design for the accelerometer.