Compared with the safe private network transmission environment for the PMU data of the main network, the transmission of the D-PMU data of the distribution network with wired + wireless communication is vulnerable to cyber attackers. This paper analyzes the characteristics of D-PMU data and reveals the principle of network attack against D-PMU data. To enhance the security of data transmission, the paper proposes a data transmission network based on cognitive radio technology and a continuous encryption algorithm for adjacent device. Simulation results verify the correctness of the proposed methods.