The present study investigated the relationship between motivational systems of investors -- behavioral activation system/behavioral inhibition system (BAS/BIS) and disposition effect, as well as the mediating effect of versatile cognitive style. Using convenience sampling method, 276 financial employees completed anonymous questionnaires regarding BAS/BIS, versatile cognitive style, and the disposition effect. The results showed that: (1) after controlling for gender, age and education, BAS-fun seeking and BIS significantly positively predict the disposition effect. (2) versatile cognitive style fully mediate the relationship between the BAS-drive and the BAS-fun seeking and the disposition effect, respectively. The results provide a reference for investors to make appropriate investment strategies according to their own characteristics.