Abstract: According to the Coulomb’s earth pressure theory,from the condition of the static equilibrium of the force when the slide wedge was in limit equilibrium,a formula was derivated for the calculation of active earth pressure of cohesive or non-cohesive backfill soils.This formula could be used in the calculation of earth pressure with superimposed load uniformly distributed on any location of ground surface behind retaining wall.Some suggestions were proposed to the calculation of earth pressure in gravity retaining wall design.