This research, based on the most active community in Taobao.com, analyzed the characteristics of transactional community in network closure mechanism. Besides, we decomposed all the data into two groups, one group includes the links sent by buyers and the other by sellers. By doing this, we can see the difference of network closure in transactional community and the different strategies conducted by buyers and sellers. The results showed: ①Buyers in transactional community would choose to avoid reciprocity because of high cost of social interaction and the risk of inefficiency of relationship, while sellers would build ties based on reciprocity since they want to attract potential and loyal customers;②In a vague situation established by strangers where informational social influence contributed the most impacts, the more options of contagion path, the more influential the member is but the less necessary the member is, which has a negative effects on getting relationship embeddedness from buyers but otherwise for sellers;③For both buyers and sellers, the relationship establishment in transactional community mainly comes from two-mode embeddedness, which includes the mutual acquaintances or mutual activities.