Abstract: Body section at a length of 340 m of left line and 290 m of right line of Xiaotiandu Tunnel is water-rich fully and strongly weathered granite stratum, which has a large deformation of excavation. Taking the above area as the object of study,exploring the construction techniques for water-rich fully and strongly weathered granite section of Xiaotiandu Tunnel,and controlling the deformation of surrounding rock. The results show that: Adopting the annular excavation of three steps reserved core soil together with advance support can control the deformation of surrounding rock effectively and reduce tunnel crown settlement;Water-rich fully and strongly weathered granite can significantly reduce its strength meeting with water, adopting the water diversion and drainage in tunnel and well-points dewatering outside of tunnel can reduce the water content of surrounding rock effectively,and then reduce the risk of water collapse effectively,guaranteeing the safety and schedule of tunnel construction. The obtained results can provide reference for the construction of large cross section tunnel under similar geological conditions.