A new secure communication method based on chaotic modulation is proposed. The parameter of the transmitting system procreated chaotic carrier is modulated by errors from an adaptive controller and information signal. At the same time, the information is directly multiplied by the chaotic carrier in transmission to drive the receiving system. In the receiver, another adaptive controller is used to maintain chaotic synchronization of the transmitting and receiving systems and to recover information signal. Since the synchronization error is independent of information signal,the chaotic modulation for large-amplitude and fast-varying information signals can be achieved. The results of theoretic analysis and numerical simulation show that the proposed method enhances the degree of security of low-dimensional chaotic systems.