Abstract: The paper investigates the chaotic synchronization of the unified chaotic system and its application to secure communication.Based on Lyapunov stability theory and linear matrix inequality method,an output feedback controller with simple structure,small feedback gain and less conservation is presented.The unified chaotic systems with unmeasurable states are synchronized,and good chaotic synchronization is achieved.Then this method is applied to secure communication through chaotic masking.Simulation is made on Lorenz system,a specific example of unified chaotic system,and the simulation results show that the method can realize asymptotical synchronization.With the presented method is applied to secure communication,the information signal can be concealed and recovered.