Abstract: During the digging construction process of diversion tunnel in Hua Neng BaoXing Power Station, the upper segment encountered the fault zone T65. Due to the emergence of this fault zone,this part has experienced a sudden mud burst and water burst for four times, seriously affecting the progress of the works. This article focuses on the engineering characteristic of this fault zone from the point of engineering geology, and uses full-face curtain grouting combined with ahead small catheter grouting technology to make the fault zone which is rich in water and mud reinforced and water-proofed, and adopts the meathod of step-by-step short footage excavation and timely support in the construction process, ensuring the safety of the tunnel construction in the result. The effective implementation of the measures sets a good example for the construction of similar projects .