In this paper, rock is treated as a kind of granular materials. The failure zone, stress and strain in surrounding rock of the tunnel are simulated by using two kinds of models. The first model is a continuum model, where granulae, interfaces and matrixes are considered. The second model is based on the first model and the matrix elements are deleted. The results show that the loop and radial stresses in surrounding rock of the tunnel fluctuate around traditional results as the strength of matrix elements is decreased slightly. As the strength of matrix elements is decreased greatly, the fluctuation amplitude rises. This result is obviously different from the result in the second model in which several loop regions with higher strains are found.