A method for adaptively allocating resources of an uplink control channel according to a system situation is disclosed. If a base station (BS) recognizes the system situation, establishes control information for resource allocation, and transmits the control information to a mobile station (MS), the mobile station (MS) allocates resources for transmitting uplink control information using a specific block or a specific resource distribution method according to the corresponding control information. The system situation may be changed according to the number of users contained in the BS s coverage or the usage of a multi- antenna. The variation of the system situation is actively reflected so that the uplink channel resources can be effectively used.