The proof mass of micromechanical silicon oscillating accelerometer is small in size and light in weight, which badly restricts the improvement of accelerometer sensitivity. So a method of using micro leverage mechanisms to amplify the inertia force is widely accepted. There are restraints existing in the input and output beam end of the leverage mechanism, and the whole structure is flexible body. Therefore the Card Theorem is adopted to deduce the theoretical formula of the leverage amplification factor. The finite element analysis (FEA) is conducted to verify the theoretical formula. Then optimize the leverage mechanics with the complex optimal method to get the reasonable design parameters of the leverage mechanism. Finally, another simulation is conducted to test the optimized result.