This paper analyzed online political participation by instrumental and psychological approach, considering impact of micro-blog usage. The study constructed three evaluation index system about instrumental usage factors, political psychological factors and online political participation degree. By a survey on university students, the Pearson correlation analysis was conducted among the factors of above three index system. At last, the paper came up with the complexity of correlations between micro-blog usage and political participation, and the positive correlations between psychological factors and political participation. High-level usage of micro-blog does not means high-level political participation. Psychological factors in media contact play more important role in political participation.