Ecological dredging has gained some consensus as an important mean of lake sediment pollution treatment.But there is no uniform standard for dredging depth design.Taking a project as an example,we analyze the polluted sediment and compare common methods including sedimentology,background value,inflection point and stratified release rate method,suggest a comprehensive coefficient K for the clearance degree of pollution transition layer to improve the dredging design method.This design method can be extended to the entire engineering area for the environmental dredging depth design.It will not only reduce the work of large-scale laboratory analysis and the cost of engineering research,but also is more convenient for application in the engineering design.