Based on the principle of light intensity modulation and micro-electromechanical system (MEMS) technology, we design a kind of optical fiber acceleration sensor. Two silicon rectangular beams are used as the acceleration sensing elements. According to the relation between the shade displacement and the light power difference of the receiving optical fiber, as well as the relation between the deflection of the silicon rectangular beam at center position and the system acceleration, an expression of acceleration with the light power difference is given. The research result shows that, while the deflection of the silicon rectangular beam at center position is 0~10 μm, the corresponding acceleration value is 0~120 m·s -2, and the maximum acceleration detective value can be as much as 12g (g is the acceleration of gravity).