Currently, the limit analysis method, the limit equilibrium method, and the numerical analysis method are mainly adopted for the slope stability analysis in the engineering field. All the three methods focus more on the overall stability and could not take the local gradual failure process of the slope into consideration. To obtain the overall research of the stability of slopes under dynamic load, the safety factor of the slope point from the displacement equivalent surface could be defined, the stress-strain relationship of the unit body could be analysed and the actual sliding direction of the slope could be taken into consideration. Moreover, the overall as well as the local stability of the slope could be derived simultaneously and a discriminative method which could reflect the critical state of the slope instability could be proposed. With the help of FLAC3D, the strength reduction method is operated to continuously reduce the shear strength of rock and soil. Moreover, the gradual instability process of slope under dynamic load is simulated and the curve of 'point safety factor penetration-reduction factor' is established. The safety factor of the slope under dynamic load is defined as the reduction factor corresponding to the penetration of the local point safety factor as well. What’s more, by analysing the location of the most critical sliding surface of the slope under dynamic load, the supporting structure of the anchor frame beam could be designed and the slope failure mode, the dynamic response of the anchor frame beam as well as the variation of the slope safety factor should be analysed. To sum up, the research demonstrates that: (1) the method is based on the development direction of slope failure and with the integration of the unit stress-strain relationship, the progressive slope failure process could be characterized and the overall and local stability of the slope could be reflected. This shows great significance to the design of the support; (2)The transfixion criterion of the local point safety factor is similar to the safety factor obtained by slope displacement criterion as well as Bishop pseudo-static method, which could be used as one of the criteria for the overall instability of slope under dynamic load. (3) The anchor frame beam could effectively improve the overall stability of the slope and reduce the local failure of the slope. Moreover, the sliding surface changes from shallow to deep.