This paper is to analyze the stability with anti-slide pile reinforced slope and determine the critical failure surface, optimal pile position and pile length. Firstly, a numerical model of slope was established based on the finite element limit analysis software OptumG2. Secondly, two cases were employed to verify the rationality of the numerical analysis. Then, the differences between two different analysis types (gravity multiplier and strength reduction) of OptumG2 were discussed based on the comparison results and the safety factor based on the strength reduction limit analysis was biased towards safety. Finally, the effects of slope angle and soil shear strength (internal friction angle and cohesion) on safety factor, optimal pile position and pile length were investigated. In addition, the variation law of the critical failure surface of anti-slide pile reinforced slope was analyzed and the fitting equation of safety factor was derived based on the parametric study results. Some regular conclusions were presented, and four common sliding surface forms and their forming conditions were summarized. The results can provide reference for the subsequent theoretical research of slope stability analysis.