The 5G network has creatively designed the network architecture and defined a completely new service network architecture. It is based on four system design principles, including IT- oriented, Internet- based, simplistic, and serviceoriented. It refers to the industry’s mature SOA, micro-service architecture and other concepts, combined with the current status, characteristics and trends of the telecommunications network. This means that the 5Gnetworks are really beginning to become open, service- oriented, and software- oriented, which is conducive to the integration of 5G and vertical industries. This paper analyzes the necessity and inevitability of architecture evolution from the aspects of requirements and technology, and then elaborates the main parts of service architecture design, including architecture reconstruction, service framework, micro service design and IT-oriented SBI. Finally, a distributed service architecture with more efficient, flexible and decoupled is proposed.