Based on the idea of active control and the Lyapunov stability theory, an active controller is designed to synchronize two different chaotic systems (the unified chaotic system and Qi chaotic system). Moreover, the fast adaptive synchronization is achieved between the drive system and the response system with different structures and unknown parameters. The results are then applied to the secure communication based on chaotic masking and chaotic spread spectrum. The MATLAB is used for the numerical simulations. The simulation results show that the method can realize synchronization of two different chaotic systems and the useful signal can be recovered effectively in the receiver during the secure communication.