On the basis of the Assumption of Mononobe -Okabe theory，the first -order differential equation for active earth pressure on the retaining wall was set up for the translation (T) mode，movement modes of rotation around base (RB) and rotation around top (RT) by analyzing slice elements extracted from the sliding soil wedge. And the formulas for calculating the unit earth pressure，the resultant earth pressure and the action point of the result pressure were given．The comparison between calculated results with the present formulas and Mononobe -Okabe theory has shown that the unit earth pressure is nonlinearly distributed；and that the distance from the action point of resultant pressure to the base of wall increases with the order of(RB)mode，(T) mode，and (RT) mode．It has also indicated that the calculated results of the resultant pressure under various modes of movement are in accordance with those of Mononobe -Okabe theory for q 0=0 .