In order to improve the sensitivity of accelerometer and meet the needs of high-precision measurement,it is very important to improve the sensitivity of optical sensing structure. A theoretical design of a novel grating-based accelerometer is proposed. The mathematical model is established and the optical properties of the structure are analyzed. The formula of the optical intensity is given,and the curve of the optical intensity variation is figured with Matlab. The main factors of the sensitivity are analyzed. Through changing the parameters of the structure,the sensitivity of the optical sensor is improved. An experimental demonstration experiment is built and the correctness of the theoretical analysis is verified.