Abstract: Fiber Bragg grating（FBG）sensors have the characteristics of anti-electromagnetic interference,no power supply,corrosion resistance and high sensitivity. As a common construction structure in water conservancy industry,diversion tunnel has some hidden safety problems due to its structure,engineering and environment. Therefore,it is necessary to carry out long-term effective stability monitoring. Based on the water supply engineering of 7# tunnel in Gansu province as an example,the optical fiber sensing technology was introduced in the safety monitoring of the diversion tunnel structure. FBG sensors were used in different encapsulation structure to monitor the stress,the displacement,the temperature,and the settlement of the tunnel effectively. The measured data also verified the reliability of the application of optical fiber sensing technology in tunnels.