Online group-buying means that a crowd of consumers combine with each other and massively purchase a certain object, and therefore can attain to a lower price(Kauffman et al. 2002). In group-buying transaction model, consumers usually recognized the risks specially. Therefore, the feedback mechanisms were used to reduce the risks and increase the trust. In general electronic shopping, many past studies especially explore the use of feedback mechanisms(Dellarocas 2003; Singh et al. 1991). However, there are few studies about the effect of feedback mechanisms on online group-buying. Compare to general electronic shopping, shopping in group-buying will include more uncertainty and risk. Thus, this study will use experimental methodology to explore the feedback mechanisms that how to impact the behavior of group-buying consumers with forum and rating feedback mechanisms. Our study mainly explores whether the feedback mechanisms affect the consumers¡¦ trust in seller¡¦s credibility and perceived risk in group-buying, and whether the intention to join group-buying is influenced by the trust in seller¡¦s credibility and perceived risk. The study shows that the online group-buying consumer behavior is influenced by the feedback mechanisms exactly. The ratings affect consumers¡¦ perceived financial risk, perceived time risk and perceived psychological risk. The forum affect consumer¡¦s psychological risk perceived, and the experience of the initiator who initiates group-buying also affect the consumer¡¦s time risk perceived. The intention to join group-buying is influenced by the trust in seller¡¦s credibility and perceived risk.