A fiber Bragg grating accelerometer based on the rotating beam is designed to attain high accelerated sensitivity in lowfrequency vibration. By analyzing its vibration model and MATLAB numerical calculation, the optimized structural parameters of the sensor are achieved. Its theoretical sensitivity and natural frequency are 1 725 pm/ g and 68. 4 Hz, respectively. Meanwhile, its sensitivity response characteristics are simulated by COMSOL, and the simulation results are closely consistent with the theoretical analysis. Experimental results of frequency response and amplitude characteristics indicate that when the acceleration changes from 0~ 2 g and working frequency in a range from 0. 5~ 20 Hz, their central wavelength of FBGs is linearly related to the vibration acceleration. In addition, a high sensitivity up to 1 495. 2 pm/ g and a good repeatability is achieved. The sensor has a simple and compact structure, in which the elastic energy consumption is decreased by bearing during the vibration of the cantilever beam. Therefore, its sensitivity is significantly improved. And the low-frequency vibration signals are detectable.