The collapse surface of surrounding rock induced by the excavation has significant influence on the stability and supporting structures of deep-buried tunnel since located in high in-situ stress field. Based on the assumption of curved velocity discontinuity surface, the internal dissipated power along the surface was calculated in the framework of Power-Law nonlinear failure criterion. In considering the role of supporting forces, an objective function composed of external rate of work and the internal energy rate of dissipation was constructed by using the upper bound theorem of limit analysis, and the analytical expression of collapse surface was obtained with the help of variational calculation. The effect of parameters on the collapse surface was analyzed. It is found that the height and width of the collapse block increased with the rise of nonlinear coefficient m, which illustrate that the nonlinear coefficient m has significant influence on the shape of collapse block. In the limit state, the height and width of the collapse block increase with the growth of supporting pressure.