In this paper, the problem of lag synchronization for a class of chaotic systems with unknown parameters is proposed. Based on Lyapunov stability theory, lag controller and update law of parameters are obtained. This method is simple and systemic. A new chaotic system is taken as an example to illustrate the effectiveness of this proposed method. Numerical simulation illustrates the feasibility of this technique. To demonstrate the robustness against the effective of bounded noise of the proposed control strategy, it is applied to the new system and perfect simulation results are obtained.