Abstract: The design of micromechanical structure is an important part of a MEMS capacitive accelerometer. In this paper, a MEMS capacitive accelerometer structure suspended by 4-arched-beams is designed. The mathematical model of the 4-arched-beam suspension is established, from which the structural parameters of suspension of the arched-beam are studied, and the optimal suspension parameters are obtained. Then, the natural vibration characteristics of the micro mechanical structure are analyzed by COMSOL software, and the influence of static electricity on the vibration frequency of the micro structure is studied. Results show that the designed MEMS accelerometer has the advantages of structural stability, high sensitivity in sensitive direction and tunable vibration frequency, etc., which provides theoretical reference for the manufacture of MEMS accelerometer with high performance.