According to the two kinds of expressions of the quadratic functions and the power functoin for describing the non_linear seepage flow,this paper advances that the two kinds of expressions should have identity,that is to say they can transform each other.And by means of least square method,the relational expression for the two kinds of functions to transform each other is derived.From the verification of the two kinds of particular seepage flow(laminal flow and adequate turbulent flow)and the hypothetic data,it has been shown that the relational expression can express the identity between them adequately,it can afford the references to the further research on the non_linear seepage flow.