This paper studies the relationship between the mode of group formation and decision-making performance of an uncertainty task.By setting up four groups according to their forming modes(voluntary and involuntary groups) and different structures(with a leader and without a leader),collecting data with scenario-simulated method,and analyzing of T test and MANOVA,we have found that:(1) the interactive effect exists between decision-making performance and the forming mode and the structure of group;(2) the group formed voluntarily and with a leader achieves significantly higher performance of decision-making than that of the other three groups;and(3) the heterogeneity of group members is the moderator between the social interaction in groups and the group decision-making performance.These findings are of great implications to entrepreneurial team building.