A novel optic accelerometer based on grating interference and phase generated carrier(PGC) modulation has been fabricated and tested. The reported prototype has sensitivity of above 4×10-5gn. Its dynamic range,which is relative with cantilevers of inertia system,is completely free from the limit of optical structure. In comparison with piezoelectricity and capacitive micro-electro-mechanical systems (MEMS) accelerometers,this device achieves an improvement both in resolution and dynamic range. Applying interference between ±1 refraction beams from a grating to acceleration sensing can also enhance stability and reduce the requirements on the installation of precision. The scheme proposed can also be applied to MEMS technique,which supplies a new thought for the design of high resolution and large dynamic range micro-opto-electromechanical systems (MOEMS) accelerometers.