Based on A.W.Bishop Method and Monte Carlo Method (MCM), slope structural reliability has been researched in this paper. These random variables include unit weight γ, internal friction angle φ and cohesion c of soil. The calculation result shows that the influence correlates to the contribution of random variable to skid resistance of slope structure, namely, the fluctuation of variable with great contribution can give great influence to safety factor K and failure probability Pf, and vice versa. Moreover, Pf is more sensitive to variable φ than to γ and c. In addition, if the fluctuation of above three variables has been considered simultaneously, the influence to Pf is sensitive when their fluctuation is within narrow range, but the influence is mainly controlled by variable φ when their fluctuation is within large range and this influence is nearly the result based on variable φ alone. This shows that internal friction angle φ plays the important role in slope structural reliability and shouldn’t be neglected.