Chaotic systems synchronization is the key step of chaos secure communications. The chaos synchronization must be realized if one wants to get the exact transformed information. In practice, the parameters is changable along with environment. In this paper, the synchronization of two unidirectionally coupled systems is proposed based on the adaptive technique when the parameters of the master system are completely unknown and different from those of the slave system. According to the Lyapunov stability theory, the rigorous proof is given for the stability of error system. Then the approach is applied to chaos-based secure communication. Numerical simulations are included to verify the effectiveness and feasibility of the proposed theorems.