An important problem in adaptive ICA algorithm is the opting step-size.This paper defines the measure of non-linear decorrelation which describes the separation states.On the basic of the measure non-linear decorrelation,a new ICA algorithm of adaptive step-size is presented.The algorithm divides the process of separation into three stages,in which different step-size algorithms are adopted.The simulation shows that this algorithm has both higher convergence rate and the lower steady-state error.