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.