In order to conceive and design the communication service subsystem of a DAS based on 4G broadband technology, the network access of FTU is realized by using the 4G LTE technology. For users' needs, in order to achieve the purpose of information transmission in distribution automation system, the VPDN services are adopted which provided by operators to group customers, and L2TP over IPSec technology is used to realize VPN network channel between DAS and FTU on the basis of the physical private line between the user and mobile operators. In the light of the constructed communication network, the DAS communication server software is designed, and the communicating function of data acquisition and output control is realized. The test results show that the requirements of communication function and network security have been realized at the communication subsystem.