Positive mental health of university students was a hot topic among the fields of social sciences and psychological sciences under the background of positive psychology. It was found that optimistic tendency was highly correlated with mental health. And Social support was found to be able to predict optimistic tendency significantly. However, it was not clear how the mechanism between social support and optimistic tendency worked. The purposes of this study were: (1) to explore the basic situation of optimistic tendency, the social support, sense of coherence and resilience in college students, and (2) to examine whether sense of coherence and resilience could mediate the relationship between the social support and optimistic tendency. A total sample of 2979 college students from five different colleges was drawn in one university in Shanghai, with 2217 females and 726 males, the average age was 19.33-year-old. They were gathered in the computer labs and finished the questionnaires within about 10 minutes. The questionnaire included the Social Support Rating Scale, the Resilience Scale, the Sense of Coherence (SOC- L9) scale, and the Optimistic Tendency Scale. A confirmatory factor analysis was calculated to test the common method variance. Results indicated that four-factor model (χ2/df = 9.38, p <.001) was better than single-factor model (χ2/df = 25.33, p <.001), making sure the study is accurate enough in terms of common method variance. The results showed that: (1) for the Resilience scale, the optimistic tendency scale, the sense of coherence scale, the social support scale, the students generally scored over and above medium level. A significant gender difference was found for in the social support scale（t=10.38，p<0.01）, the sense of coherence scale（t=3.19，p<0.01）, the optimistic tendency scale （t=5.75，p<0.01, and the resilience scale（t=5.18，p<0.01）. More specifically, the girls always got higher scores than the boys. (2) The optimistic tendency scale was positively correlated with the social support scale（r=0.29, p<0.01, the sense of coherence scale（r=0.34, p<0.01, and the resilience scale（r=0.35, p<0.01）. (3) A structural equation model (SEM) revealed that the model fitted the data well (χ2 /df= 36.8, p <.001, NFI=.984, CFI =.984, IFI =.980). Social support significantly predicted sense of coherence and resilience in college students. Sense of coherence and resilience had multiple intermediary effects on social support and optimistic tendency. Sense of coherence mediated the relationship between social support and optimistic tendency. It was concluded that the social support had directly influence on optimistic tendency, and sense of coherence and resilience had multiple intermediary effects on optimistic tendency in college students. Optimistic tendency took an important role of on the improvement of students' mental health. These findings suggest that measures of resilience could be used along with measures of social support and sense of coherence to detect students at-risk for mental health problem and that intervention programs targeting resilience as well as social support could be developed to improve university students’ positive mental health.