Taking a diversion tunnel as engineering background, the paper applied Unwedge program and took the rock mass of key block as a target to choose the reasonable direction of tunnel and type of excavated section.Meanwhile,it took No.6 block of left wall as the research object,and safety coefficient as evaluation indicator, and carried out sensitivity analysis on six parameters and the highest sensitivity of cohesion Sc is 0.922 which has the greatest influence on engineering stability and the lowest sensitivity of internal friction angle Sf is 0.002 which has the least influence on engineering stability.Therefore, the sensitivity calculation of mechanics parameter for wall rock can provide the basis for designer to reasonably determine the precision of parameter value.