This study aimed to apply psychological strain theory to explore the relationship between psychological strain and suicidality among Chinese young adults with a moderating effect of perceived social support. A questionnaire was administered with the Multidimensional Scale of Perceived Social Support, Suicidal Behaviors Questionnaire-Revised, and Psychological Strain Scale among 13,250 college students across China. The main determinants of suicidal behavior were examined with multiple linear regression. Two steps of multiple regression were employed to define the moderating effect of social support. A positive relationship between psychological strain and suicidality was reported in the study, and social support was confirmed as a moderating factor between psychological strain and suicidal behavior.