A new type microaccelerometer with magnetorheological (MR) fluids is presented in this paper. MR fluids can easily change from a fluid state to a semi-solid state in milliseconds when exposed to magnetic field. They are applied to the microaccelerometer where the MR fluids can vary the relative dielectric constant and provide damping. Then the electrostatic force has been adopted in the microaccelerometer for balancing force. Therefore, the measurement range of the microaccelerometer will be expanded. The mathematical model of the microaccelerometer with MR fluids is derived. The curve of the accelerometer between the deflection of the silicon doubly-supported beam and voltage has been simulated. The curves of the accelerometer between the voltage and the acceleration are also got. Last, the stability of the microaccelerometer system has been analyzed.