Abstract: Objective To explore the mediating effect of rumination on coping style and insomnia in college students. Method We surveyed 767 college students from a university in Sichuan Province using Insomnia Severity Index (ISI), Ruminative Responses Scale (RRS), and Trait Coping Style Questionnaire (TCSQ). Results The prevalence of insomnia was 36.6% in the surveyed college students. Positive coping style was negatively correlated with the total score and scores in each dimension of RRS (r=-0.127~-0.116, P<0.001), and was negatively correlated with the total score of ISI (r=-0.159, P<0.001). Negative coping style was positively correlated with the total score and the scores in each dimension of RRS (r=0.298-0.334, P<0.001), and was positively correlated with the total score of ISI (r=0.264, P<0.001). The total score and the scores in each dimension of RRS were positively correlated with the total score of ISI (r=0.251-0.281, P<0.001). Rumination had a partial mediating effect on both positive and negative coping style and insomnia. Conclusion Coping style affects insomnia in college students not only directly but also indirectly through the mediating effect of rumination.