Abstract: The existence of many cavities behind the tunnel secondary lining will lead to the deterioration of the structural stress conditions, which could easily cause tunnel lining cracking and even directly affect the operation safety of tunnels. In this context, the method of grouting through molds is widely used at construction sites to fill the cavities. In order to study the changing pattern of the bearing capacity of the lining structure during the grouting via molds, aiming at elimination of cavities behind tunnel secondary lining, the lab model tests are conducted with geometric similarity ratio of 1∶30, in combination with the engineering condition of a railway tunnel which uses microexpansion materials for grouting and reinforcement of secondary lining cavities, and the force distribution pattern and characteristics of the initial support and the secondary lining are studied in terms of grouting and reinforcement at different cavity locations behind the secondary lining with high-performance micro-expansion filling materials. The results show that the bending moment at the cavities grows fastest, and the growth of the bending moment in the secondary lining is greater than that of the initial support, with the most obvious growth at the cavities of the vault and the cavities of the double-arch shoulder; the axial force at the cavities grows fastest and changes most significantly at the top of the arch and the right arch shoulder. The internal force changes of the structure caused by the filling materials during the grouting process are within the specified range and no cracking is found, which effectively verifies the application safety of the self-developed cement-based filling materials.