Abstract:Abstract: sericite schist is a kind of complex soft rock in southwest China, which is easy to soften and muddy when exposed to water. Large deformation of soft rock is a common problem in tunnel construction under this stratum. Improper treatment will also cause collapse, which is extremely easy to cause serious consequences. In this paper, the deformation and stress characteristics of sericite schist tunnel are studied by field tests with practical engineering as the carrier. The results show that the three-step excavation leads to the multi-stage release of the surrounding rock pressure. After each step excavation, the surrounding rock pressure goes through two stages of rapid increase and slow increase, and the surrounding rock pressure generally presents an asymmetric distribution of "larger right upper and lower left, and smaller right lower and upper left". The steel arch is dominated by compression, and the stress distribution is "large in the top and small in the bottom". The compression stress of the steel frame at the right arch waist is 237.4 Mpa, which is greater than the designed value of the steel frame"s compressive strength. As the surrounding rock is extruded inward as a whole, the tunnel presents the asymmetric deformation of "big on the top and small on the bottom". The maximum deformation at the right arch waist is 325 mm, larger than the reserved deformation. The study points out the hidden danger in the construction process, and provides data reference for the design and construction of sericite schist tunnel.