A method of power reporting for a mobile device configured with a plurality of uplink component carriers and/or parallel PUCCH and PUSCH transmission in a wireless communication system is disclosed. The method comprises being configured a maximum output power for at least a uplink component carrier, determining to start or stop a maximum output power reporting for the at least a uplink component carrier according to a characteristic associated to the mobile device or a network of the wireless communication system, and reporting the maximum output power for the at least a uplink component carrier to the network when the maximum output power reporting is triggered and the maximum output power reporting is started.