An online game service system for randomly allocating game channels according to user behavior patterns includes a user behavior pattern database, a channel database, a channel server, and a game server so that users having the same or similar game behavior patterns may play games. The user behavior pattern database stores behavior pattern classification references and user game behavior patterns. The channel database stores a list of random channels and data on game rooms at the random channels. The channel server selects a random channel according to the user behavior pattern, provides data on game rooms generated in the selected random channel, and controls a user to enter a game room. The game server provides a game service to the users having entered game rooms, determines game behavior patterns of the users by using behavior pattern references, and stores the determined game behavior patterns in the user behavior pattern database.