Abstract: Based on sliding plane hypothesis of Coulumb earth pressure theory,Coulumb accurate solution of active earth pressure to cohesive soil was improved which considered the cohesion force on sliding surface and the adhesive force on interface of retaining wall.The improved method is simple to handle load on soil surface and calculate crack depth.Only taking Z0 to be the equal of zero,the calculation formula without considering crack on soil surface is the same as those considering crack completely.The formula is reliable and convenient.It is easy to popularize and apply for projects.