The stability of a layered rock slope is affected by many factors,such as slope height, slope angle, structural plane strength, and so on. The degrees of influence of such factors vary, and in most cases, depend on the comprehensive judgment generated from an actual engineering exploration. In an orthogonal experiment that features two main parameters (factors and levels), a factor refers to the set of elements that may directly affect the results of a test and may be single or multiple. The level of factor refers to the specific value of the human factors in the experiment. This paper analyzes the sensitivity of the main factor, which affects the stability of the rock slope and determines the composition of the primary factor as follows: the slope height H>slope angle β > structural surface cohesion C > structural surface friction angle φ > rock density γ > the dip angle α > block thickness h > rock cohesion. Next, we discuss the efficiency of the finite element method in determining slope accuracy, which is also an important factor that can affect the stability of a slope. By taking the numerical calculation of the rock slope of a typical single line sliding surface as an example, the influences of element mesh size and boundary condition on the safety factor of slope stability is analyzed. Some numerical simulation suggestions are proposed according to the calculation results, and these suggestions are used to improve the accuracy of the numerical calculation of the known sliding surface rock slope. In general, the common sliding surface application of 20~30 in the interface unit is enough, and the mesh size is roughly set at 2~3 m to meet the accuracy requirements. We also find that the smaller the mesh size is, the longer the time required, although the safety factor only showed a slight change. There should be at least three or four layer elements under the potential sliding surface to ensure the transition to the fixed support boundary. According to the preliminary forecast, in order to prevent the wave reflection at the interface, element size should be controlled in the λ/10~12 (where λ is the wavelength), because of the encryption unit within the analysis of dynamic stability of slope, thus increasing the scope of the model.