The essence of online group-buying is to lower the price by gathering orders However, the process is filled with uncertainty and risks, such as the number of joining members, the final price, the quality of products, and even the trustworthiness of the initiators. Generally speaking, consumers tend to reduce risks by searching more information. The more uncertainties there are, the more information seeking should be. Online feedback mechanism is often adopted as a strategy to lower risks and uncertainties. Both e-Bay and Yahoo provide such feedback mechanisms. In addition, the larger the number of accumulated orders is, the higher possibilities to lower the price and risk will be. Therefore, the purpose of this research is to explore how the online feedback mechanism and the number of accumulated orders impact consumers¡¦ perceived risk and trust in the initiator and furthermore, how the perceived risk and trust impact consumers¡¦ behavior in online group buying. The study shows that the content of the online feedback mechanism has significant impact on consumers¡¦ perceived financial risk, performance risk, total risk and the trust in initiator as well. The more negative the content is, the more risks the consumers perceive and the less trust in the initiators the consumers have. Furthermore, different contents will result in different kinds of risks perceived by consumers. With larger number of accumulated orders, consumers have more trust in initiators. Additionally, consumers have higher intentions to join group-buying when they perceive lower risk and more trust in initiators. Therefore, consumers¡¦ intentions to join group-buying have significant impact on their actual behavior.