Objective To investigate the relationship between negative cognitive bias and social anxiety in serviceman, and to understand the mediating role of fear of evaluation. Methods A total of 878 officers and soldiers were randomly selected from a naval force. The fear of positive evaluation (FPE), fear of negative evaluation (FNE), negative cognitive bias and social anxiety levels were measured by fear of positive evaluation scale (FPES), brief fear of negative evaluation scale (BFNES), negative cognitive processing bias questionnaire and interaction anxiousness scale (IAS). Structural equation model was used to test the mediating role of fear of evaluation. Results The correlation analysis showed that the scores of 4 dimensions (negative attention bias, negative memory bias, negative interpretation bias and negative rumination bias) and total scores of negative cognitive processing bias questionnaire were positively associated with the scores of FPES, BFNES and IAS (all P<0.01). The mediating effect tested by structural equation model showed that the fear of evaluation played a partial mediating role, the indirect effect was 0.31, 95% confidence interval (CI) 0.26-0.35, and FPE and FNE were independent of each other. Conclusion Soldiers' fear of evaluation plays a mediating role in the relationship between cognitive bias and social anxiety, and soldiers should correctly treat others' comments.