Information spreads quickly on social networking platform. In order to effectively carry out public opinion early warning and quantitatively evaluate the importance of users in social network, the fuzzy comprehensive evaluation method is introduced into the user influence modeling problem. Based on the analysis of the behavioral analysis of the user's behavior on the social platform, the evaluation system including five indicators, such as user active number of fans and average forwarding number is constructed. A new fuzzy synthesis operator is proposed to construct the user influence evaluation model based on the shortcomings of the traditional fuzzy comprehensive evaluation algorithm in calculating the weight of the evaluation index. This operator can adjust the weight of the impact on the evaluation results according to the demand. Using the real data of Sina microblogging social platform, combined with comparative experiments and practical assessment, the method can more accurately reflect the actual impact of the user in the social network.