Objective:To explore the role of mindfulness and negative cognitive bias between behavioral inhibition system and social anxiety among college students.Methods:From October 12th to November 8th of 2012, a total of 747 college students from a university in Tianjin were sampled and assessed using the behavioral inhibition system scale (BIS), the mindful attention awareness scale (MAAS), the negative cognitive processing bias questionnaire (NCPBQ), and the social avoidance and distress scale (SAD). Descriptive statistics, correlation analysis, and tests for mediating effects were performed by SPSS 20.0 and Mplus 8.0.Results:The scores of behavioral inhibition system, social anxiety, mindfulness and negative cognitive bias were (15.3±2.4), (12.7±7.2), (3.4±0.8) and (45.6±11.5), respectively. The scores of BIS, NCPBQ, and SAD were positively correlated with each other ( r=0.27-0.49, all P<0.001). The scores of MAAS were negatively correlated with the scores of BIS, NCBPQ, and SAD ( r=-0.33--0.28, all P<0.001). The behavioral inhibition system exerted its influence on social anxiety through three pathways. The mediating effect size of mindfulness was 0.04, accounting for 16.0% of the total effect. The mediating effect size of negative cognitive bias was 0.17, accounting for 68.0% of the total effect. And the chain mediating effect size of mindfulness and negative cognitive bias was 0.04, accounting for 16.0% of the total effect. Conclusion:The effects of behavioral inhibition system on social anxiety in college students are individually mediated by mindfulness and negative cognitive biases, as well as their chain mediating effects.