Abstract: As the weak structural surface of rock mass, the joint plane significantly affects the stability of tunnel surrounding rocks, and the chip off-falling at crown, collapse and slippage are more likely to occur for the largespan tunnel with many joints. Taking the Nanyalu No.3 tunnel in Guiyang as the background, it analyzes the safety factors in conditions of different joint angles, joint spacings, set numbers and lining parameters by distinct element based strength reduction method in 3DEC software, and evaluates the effects of various factors on tunnel stability.The results show that the larger the joint angles and the joint set numbers and denser the joints, the more unstable the tunnel; the stability of tunnel is mainly effected by the joint angle for the rock mass with single set of joint;sprayed concrete layer significantly improves the tunnel stability, the safety factor of the tunnel with lining thickness of 10 cm is improved by 17.9% compared with that without any lining structure, and some optimization suggestions for the tunnel lining parameters are proposed in light of this.