In order to study the mechanical characteristics of secondary lining of large crosssection highway tunnels, an indoor similar model test is carried out. The surrounding rock pressure forced on operating tunnel is simulated by active load, and the laws of internal force, deformation and failure of secondary lining of threelane highway tunnel and broadband highway tunnel are studied. The model test results show that: (1) The internal force and deformation of secondary lining structure under loads designed by relevant codes are small; and the lining structure has large safety coefficient. (2) The section internal force (bending moment and axial force) of secondary lining increases with an accelerated speed with the increase of the surrounding rock pressure; while the eccentricity decreases gradually. (3) With the excavation area increase, the number of risky crosssection increases. (4) Excavation crosssection size also has a certain influence on deformation and failure pattern of secondary lining; the larger the excavation crosssection is, the more obvious the deformations of crown top and sidewall and the difference of cracking loading in different parts are, and the longer the process of lining structure cracking lasts.