In the channel for which ebb and flow is obvious, how to determine the minimum embedment depth of cofferdam under the force caused by wave and flow for the desingn of the cofferdam,ensuring the construction safety has important and practical value. In this paper,the threedimensional source destribution merhod is adopted to establish the mathematical calculation model of wave force for large scale structures,and superimposed by "General code for design of highway bridge and culverts"related formula of current force, to determine the cofferdam structure for the wave flow combination reaction. And then through the actual project of the steel sheet pile cofferdam in the "strong current ,weak wave load combination "and "strong current ,strong wave load combiation "of cofferdam for the minimum depth of embedment of application examples, the feasibility of the merhod was verified. Finally , we discussed the wave flow combined with rectangular cofferdam structure displacement and angle relationship, and the factors affecting the cofferdam embedment depth make the multi-parameter analysis, and some beneficial conclusions are drawn.