Surrounding rock of Gonghe Tunnel is lamellar limestone. Its rock specimens have distinct anisotropy from complete stress-strain curve in uniaxial compression test; and yield failure of surrounding rockmass has remarkably directional property from in-situ monitoring results. According to these results and characters

selecting appropriate yield function and suitable strength parameters vary with angle between layered rockmass or maximum principal stress

combining elastic constitutive function of anisotropy; then elastoplastic constitutive function of anisotropy is obtained and implemented with C++ language. Gonghe Tunnel is numerically modeled by utilizing this constitutive function; and numerical simulation results essentially coincide with failure character. It is shown that the elastoplastic constitutive function of anisotropy is correct; and it can be used for analyzing support design and stability of the tunnel.