A micromachined tunneling accelerometer has been designed, which is based on HNA etching, ICP and p+ stop process. System model that incorporates the mechanical tunneling device and its feedback control circuitry is built. Simulations of the system present the output static and dynamic properties according to which the key parameters are optimized. In this paper the working point of the tunneling accelerometer, which is determined by the structure in company with the feedback circuitry is calculated through the system model. In this way we can forecast the whole working process of the system before the test and choose the proper parameters of the circuitry components accordingly, which greatly reduce the times of trial and error in the micromachined tunneling sensor development.