Abstract:The chemical reinforcement of rock mass is researched on the background of resisting weathering of surrounding rock at Longyou Grottoes in Zhejiang Province. Four layouts with four different chemical materials are applied in order to reinforce sandstone specimens in the laboratory. The new material of chemical reinforcement which is named CRS is put forward through the analysis of the parameters obtained from test. The CRS reinforcement test follows the principle that the voids in rocks are filled with products from the reaction between inorganic silicon and rocks first and then the rocks are dehydrated by reaction between organic silicon and hydroxyl in rocks so as to achieve the goal of reinforcement. The wave velocity,cohesion,peak strength with 5 MPa confining pressure increase 15%,50%,50% or so,respectively,and the variation of inner friction angle is not apparent after rock specimens are fully socked in the CRS material in the laboratory. The rock mass structure is apparently densified and the wave velocity of surrounding rock is increased by 10% for dry rock mass and 5% for rock mass soaked in water after the surface of grotto surrounding rock is treated by the CRS material in-situ. It is proved that the reinforcing depth is more than 3 cm. Until now for about one year the surface and inner color of rock mass has not yet obviously changed.