The influences of slope rate of rock slope and inclination angle of sliding surface on anchoring effect are investigated in this paper. ANSYS is employed used for modeling and meshing of rock slope with structural plane; FLAC^3D is used to build a known inclination of sliding surface; and finally, strength reduction method is adopted to solve the safety factor of the slope, and the functional relation between anchoring angle and safety factor in the presence of varied slope rate and inclination of sliding surface was obtained. Through fitting of the theoretical formula and the numerical simulation results, we conclude that: (1) In rock slope, through theoretical deduction, the optimal anchorage angle is defined as the anchorage angle corresponding to the maximum anti-sliding force in the free section of the anchor. (2) When the slope rate is known, anchorage angle is in a negative correlation with safety factor, which suggest that safety factor decreases gradually with the increase of anchorage angle. When the inclination angle of sliding surface is known, the safety factor of slope declines with the increase of slope rate in the presence of the optimum anchorage angle. (3) When the inclination angle of sliding surface is known, anchorage angle has a negative correlation with safety factor, implying that safety factor reduces gradually with the augment of anchorage angle. When slope ratio is known, safety factor drops first and then rises with the increase of inclination angle in the presence of the optimum anchorage angle.