The effect of strip surcharge on the inclination of sliding plane of soils behind retaining wall is taken into account. New formulas of active earth pressure due to strip surcharge are presented based on Coulomb’s theory. When the surcharge is zero

the formulae are the same as Coulomb’s theory. If the strip surcharge is cut by the sliding plane of soils

it is shown that the obliquity of sliding plane of soils behind the wall is not only related to the angle of internal friction of soil

the angle of wall friction and the inclination of ground

but also to the magnitude of surcharge and the distance of the surcharge from the wall. It is also shown that the farther the surcharge from the wall

the smaller the coefficient of active earth pressure. The bigger the magnitude of strip surcharge

the bigger the coefficient of active earth pressure.