It is very important to calculate the active earth pressure of cantilever retaining wall under earthquake. To analyze the active earth pressure distribution of cantilever retaining wall under seismic load,by applying the proposed dynamic method and considering the impact of variation of horizontal and vertical earthquake force on seismic active earth pressure, the calculating formulas of the critical Angle of rupture and seismic active earth pressure were deduced,and the influence of parameters on the seismic active earth pressure coefficient and the critical Angle of rupture were also investigated. The results show that the second critical fracture Angle increases with the increase of the vertical seismic force coefficient and decreases with the increase of the horizontal seismic force coefficient. The active earth pressure increases with the increase of horizontal and vertical seismic force coefficients.