Micromechanical resonant sensors are very attractive for high-precision measurement applications due to their high sensitivity, direct frequency output and large dynamic range. This paper presents a high accuracy micromechanical resonant accelerometer on basis of detailed investigation. The structure includes a substrate, a proof mass, cantilevers, leverage mechanisms, resonant beam, tuning forks, driving poles and checking poles. Due to the box-shaped structure of proof mass, a larger inertial force generated by the proof mass can be achieved. DETF (double-ended tuning fork) resonator is the simplest form of stress sensitive dynamically balanced structure that can reduce the common mode interference. There are comb electrodes on both sides of the DETF, which are used to actuate the DETF and sense its amplitude in resonant state. Differential output is achieved by two tuning forks that are symmetrical distributed and the energy output is two times that of one double-ended tuning fork. This kind of structure can also reduce the co-model disturbance. The structure parameters and capability parameters are calculated by MATLAB, and mechanical and model analysis are carried out by ANSYS. Simulating results show that the design is available and the structure can satisfy the design demands.