Abstract: Grouting is an effective method to guarantee the smooth advancement of tunnel construction. Tunnel grouting theory is expounded from the aspects of percolation threshold effect, fracturing grouting mechanism and fluctuating grouting pressure. New grouting materials are analyzed and discussed combined with both polymer and microbial liquid, and a numerical simulation calculation of tunnel grouting is carried out by Comsol finite element method and PFC (particle flow code) discrete element method. Results show that the percolation threshold effect leads to the deposition of cement particles on the pore channel and clogging, severely affecting the reinforcement effect of the diffusion distal end. The fracturing and fluctuating grouting are suitable for improvement treatment of the geomaterials under complex conditions. Representing the new materials, high polymer and microbial liquid will be the development direction of grouting technology in the future, while numerical simulation will become an important supporting means for grouting technology research because of the low cost and high efficiency.