Consumers can obtain cheaper goods through collaboration. However, it’s very difficult to find a certain group of people with the same demand in traditional markets. Internet makes this dream come true. Customers with mutual interests can get together easily and bargain with manufacturers by using the power of group. This paper presents a coalition formation mechanism which is based on Negotiation-Credit Based Negotiation. Buyers and sellers can bargain with different strategies, which also founding on Negotiation Credit, and close deals more efficiency. The concept of group buy could be extended to group sell and enhance the market function.