Abstract: In recent years, chaotic synchronization has become an area of active research, especially in light of its potential application to secure communications In this paper, the synchronization of a coupled delayed neuron chaotic system is investigated The asymptotic stability of the synchronization is analyzed based on the Krasovskii Lyapunov theory, and a sufficient condition of synchronization is obtained Furthermore, the synchronization threshold of the coupled system is estimated The results of computer numerical simulation show that the proposed synchronization system is an effective one, which is robust when Gaussian white noise N （0,0 0005） is added, and the simulation result is consistent with the theory analysis Finally, an application example is given, which uses the proposed chaotic system to realize spread spectrum secure communications based on the chaotic masking strategy The advantage of this application system is that synchronization can be achieved by transmitting just a single scalar variable Because this scalar variable is used to directly drive a receiver, and possesses broadband power spectra property, so this makes it difficult to detect or predict the signal in either the time or frequency domain, and the communication system is more secure consequently