A method and a user equipment (UE) for receiving a power headroom report in a wireless access system that supports a carrier aggregation are discussed. The method according to an embodiment includes transmitting by an eNB to a UE an uplink transmission grant allocating uplink resources on a predetermined subframe in an anchor uplink component carrier (UL CC); and receiving the power headroom report by the eNB from the UE. The power headroom report includes a power headroom value for the anchor UL CC, when the eNB has configured the UE for a simultaneous physical uplink control channel (PUCCH) and physical uplink shared channel (PUSCH) transmission. The method further includes reporting the power headroom value to a base station. The power headroom value is calculated.