Transportation properties of composite under a strongly applied fie1d satisfy the nonlinear constitutive relationship. It is rather complicated to evaluate the conductivity of nonlinear composite. In the theory of linear composite, various methods have been developed under concept of effective medium approximation (EMA), which offers neat analytic formulae for evaluating effective transportation coefficients. Methods of EMA give reliable theoretical predictions, if particle concentration is beyond the percolation threshold and conductivity contrast is finite, Therefore, the EMA is a useful tool for technology applications. Based on perturbation expansion method for nonlinear composite, a new nonlinear EMA is proposed in this paper, which coincides well with generalized Landau formula at low particle concentration.