A method for inviting an Instant Messaging (IM) user to join an online game is provided. An inviter generates a first instant message according to an online game selected by an inviter user, and sends the message to an invitee, where the first instant message contains description information describing the online game selected by the inviter user; after receiving an instant confining message returned by the invitee, which indicates that the invitee user agrees to join, the inviter requests according to the description information of the online game selected by the inviter user the game server of the online game to allocate game resources; after the game server successfully allocates the game resources, the inviter and the invitee respectively add the inviter user and the invitee user to the online game provided by the game server. The inviter is thus prevented from performing unnecessary operations.