Mononobe-Okabe theory is a widely used method to calculate seismic earth pressure at present; but some hypotheses of which have certain limitations. In light of the deficiency of Mononobe-Okabe theory

and considering the effect of retaining wall deflection on earth pressure

the diagonal slice method is used to deduce the strength distribution of seismic cohesive earth pressure under complex states; earth pressure resultant and its action point. The analytical solution of critical rupture angle is given with graphical method. Research results show that fill cohesion and seismic coefficient influence earth pressure signally; ignoring the surface cracking of cohesive fill and the impact of the earthquake on the uniform overload and the crack fill equivalent overload would make the result of active earth pressure turn small

whose deviation would turn big as fill cohesion and uniform overload goes up; earth pressure is in linear distribution along the height of wall in different horizontal seismic coefficients; the given formula fits wider situations

and effectively improves the Mononobe-Okabe theory.