According to the characteristics of the geosound of de bris flow,a cantilever acceleration sensor based on fiber Bragg grating (FBG) is proposed.The influencing factors o f the sensitivity and the resonant frequency of the sensor are analyzed theoretically,and the key structure parame ters of the sensor are optimized by experiments.Moreover,some new technologies,such as the anti-bending optical fiber,the super thin coating with polymer material and the FBG charge coupled device (CCD) demodulation,are used to improve the sensitivity and the serial multiplexing performance of the sensor.At last,a simple comparison test is carried out in the field. Experimental results show that the sensor with the sensitivity of 400pm/g and the natural frequency of 310Hz as a kind of accelerometer with excellent performance can be expected to be better appli ed to the ground monitoring.