Abstract: In an online group-buying method, a server sends a group-buying invitation message, which includes shop information associated with a seller terminal, to an invitee terminal in an invitee list in response to a group-buying invitation request message from an inviter terminal. Upon receipt of a join message and a purchase order, which is associated with one or more products provided by the seller terminal, from the invitee terminal, the server sends the join message and the purchase order to the inviter terminal. Then, the inviter terminal sends an integrated purchase order, which is generated according to at least the purchase order, to the seller terminal.