Based on both positive psychology and the gene × environment research paradigm, the current study constructed a moderated mediation model to explore the relationship between childhood maltreatment and college students' depression symptoms. The sample comprised 301 college students (74 males and 227 females; average age = 19.15 ± 0.63 years of age, age range 17 to 20). The results indicated that: (1) Childhood maltreatment had a significant positive correlation with college students' depression symptoms, and subjective well-being had a significant negative correlation with childhood maltreatment and college students' depression symptoms; (2) Subjective well-being appeared to play a mediating role in the relationship between childhood maltreatment and college students' depression symptoms; (3) The MAOA gene rs6323 polymorphism moderated the indirect path from subjective well-being and college students' depression symptoms.