In this paper, we focus to design and simulation of a piezoresistive accelerometer using three different soft-wares corresponding to three different levels: system, device, and physical ones. At the system level, MATLAB software was utilized to model a simple mechanical damping system. At the device level, we have used SUGAR/MATLAB to investigate the basic behaviors of 3-DOF accelerometer. Consequently, the ANSYS finite-element software has been used to design and simulate the advance properties of a 3-DOF piezoresistive accelerometer. At this level, we would also perform optimization process for the fabrication step.