The quality of expert is the key factor affecting the level of think tank's research and decision-making consultation. In this paper, 448 fields about experts of CTTI system are extracted to construct a think tank expert group portrait model, which includes 3 first-level labels, such as basic attributes, academic research, social activities, and 12 second-level labels. A sample of 2150 experts with complete data in the CTTI system was obtained through data cleaning, and the characteristics of the experts were summarized by using the methods of collective biography, bibliometric analysis and social network analysis. The research found that the experts of Chinese think tanks have high academic qualifications and professional titles, they are mainly middle-aged men and doctors in humanities and social sciences, they often work part-time across institutions and collaborate less on research. Besides, they are less embedded in the decision-making process, and they don't do well in terms of public opinion influence.