Considering the influence of shear dilation on the stability of surrounding rock, mechanical performance using finite differential code was conducted for circular shallow tunnels, two-lane highway shallow tunnels and double-track railway shallow tunnels when plastic flow occurred in the surrounding rock. Under the given conditions, the displacement, plastic zone and maximum shear strain rate of circular tunnel were emphatically simulated and analyzed. The stability factor of three tunnels was computed, and the influence of dilation angle on the stability factor was analyzed. The results show that there is a critical dilation angle which impacts the displacement of surrounding rock, that the plastic zone increases with the increase of the dilation angle, that the dilation angle has important effect on the shear bond and stability factors, and that the critical stability factors change along with the change of dilation angle when the shear dilation of surrounding rock is considered.