The problem of two identical chaotic systems with noise is investigated in this article .The instantaneous mean square error(ε)is analyzed based on the Jacobian equation of the response system .A syn-chronization scheme is proposed here , and the time-varying coupling parameter sequence used in this newscheme is obtained by minimizing the instant aneous ε.Numerical simulation shows that two 2-D logistic map reach the state of synchronization with the time-varying synchronization method .