Abstract: According to the fiber bragg grating sensing principle, we design a monitoring system to measure the roof separation, and the calibration of the fiber bragg grating instrument for roof separation and the test of the system are conducted in a lab. Calibration and test results show that the separation data has high correlation with changes in the wavelength; long term stability is good. Applying the system in Shaqu Mine 14301 roadway and the practice shows that compared with the traditional measuring method, the system not only improves safety and makes the data more accurate, but also adapts to the underground environment.