In recent years, 5G has been the focus of research and development in the telecom industry. This paper aims to understand the development trend and technical hot spots of 5G technology through the patent analysis and build a citation network at the assignee organization level. The workflow of the paper is divided into four steps: patent data collection and cleaning, patent overview analysis, network creation and analysis, O-I index analysis. This article collected the patent data from the United States patent and trademark office (USPTO). We understand the application trend, technical hot spots, and leading players in the 5G domain through the patent overview analysis. We comprehend the structure and characteristics of the network and critical nodes from network topology analysis. By using O-I index analysis, we learn the flow of 5G technology knowledge between the organizations. This paper provides a useful analytical model for the patent analysis and technological knowledge flow in a specific field, which can be applied to patent analysis in other fields.