A mode frequency test method for the MEMS capacitive devices is put forward based on modulation and demodulation.The test theory and the constitution of the test system are introduced.The simulated mode frequency of a comb microaccelerometer by Ansys is 3941Hz

and the measured mode frequency of this microaccelerometer by the test system is 3440Hz

which is very close to the simulated result.So it can be concluded that the mode frequency test system works very well

and the difference between the simulated result and the measured result is mainly due to the fabrication imperfection.