Abstract: This paper presents a new method to obtain the tangential load of the bolt. Arranging fiber bragg grating on the bolt as the sensor, we arrange three fiber bragg grating strings which are mutual into 120 ° at anchor section along the axis direction of bolt. By means of the arrangement of the fiber bragg grating sensor, the position strain of the bolt under tangential load is obtained. A reasonable mechanical model is established, and the tangential load of the bolt is calculated by using the strain condition of each position of the bolt.