A fiber Bragg grating (FBG) acceleration sensor with an increased sensitivity symmetric simply supported beam structure is proposed to meet the requirements of high sensitivity vibration detection at medium and low frequencies.Firstly,theoretical analysis is conducted on the sensor model,followed by numerical optimization of the sensor structural parameters.In order to meet the requirements of high sensitivity,the thickness of the simply supported beam is only 0.5 mm.Then,finite element method is used to simulate and analyze the sensor.Finally,the actual sensor is processed and experimentally tested.The experiment shows that the resonant frequency of the sensor is 294.6 Hz,The sensitivity is 307 pm/g,and the lateral anti-interference degree is less than 2.7%.It can be used for measuring vibration signals in the frequency range of 30—130 Hz.