〔Objective〕To explore the relationship between intolerable uncertainty, social support and pessimism of the new-generation college students, and to test the moderating role of social support in the relationship between intolerance of uncertainty and pessimism. 〔Methods〕A questionnaire survey was conducted on 500 college students in Guizhou Province by using Intolerance of Uncertainty Scale, Perceived Social Support Scale, and OPS-C Scale, and 467 valid questionnaires were recovered.〔Results〕 ① The intolerance of uncertainty of the new-generation college students has a significant positive correlation with pessimism r=-0.147**(P＜0.01); ② The external value dimension of social support has moderating effects between intolerance of uncertainty and pessimism (β=0.145, t= 3.461, P＜0.05). 〔Conclusions〕① New-generation college students will have significant pessimism when they face events of intolerable uncertainty; ② When social support is stronger, the effect of intolerance of uncertainty on pessimism will be reduced, and when there is no social support or less social support in the environment, this effect vanishes.