The decoupling problem for Volterra adaptive filter is discussed in this paper.By proposing and analyzing the pseudo-linear combination structure of Volterra filter

a new MSE(mean square error) expression can be obtained.Because the Volterra adaptive filter problem can be described as a constrained optimization one

a fully decoupled Volterra normal equation with block-diagonal input correlation matrix satisfying the MMSE(minimum mean square error) criterion is educed.Then a fully decoupled Volterra filter is designed and the adaptive regulating formulation for the weight vectors of the filter is given out.Simulation results indicate that the proposed method in this paper is efficient.