The present invention is directed to a wireless communication system. More specifically, the present invention is directed to a method and an apparatus of controlling uplink transmission at a user equipment in a wireless communication system, wherein the user equipment is connected to multiple component carriers, which includes receiving configuration information for transmitting an uplink signal from a base station; and identifying a time for transmitting the uplink signal to the base station on a corresponding uplink component carrier in use of the configuration information, wherein if the corresponding uplink component carrier is in a non-available state at the time for transmitting the uplink signal, the uplink signal is not transmitted.