This study analyzes the impact of self-categorization on the overall sense of fairness and different domain of fairness of the people. The data was from CASS-Intellvision Social Mentality Survey 2017. The results showed that self-categorization couldn’t influence the public’s ranking of fairness；the impact of self-categorization on the sense of fairness may be affected by the intensity of fairness；self-categorization became a systemic bias that affected individual social cognition；different taxonomies of self-categorization had different effects on the sense of fairness. Those results suggested that people had common consensus on fairness and unfairness region，and the fairness of allocation was the lowest，which meaned that the governance should take care of income distribution reform to improve people’s sense of fairness. Those results also implied that self-categorization could affect individual’s social cognition systematically，and then induced social cognition bias.