A method and terminal device for power control in a carrier aggregation system across the eNBs includes: a UE receiving semi-static power control parameters, as well as transmission power control commands TPC, from PCell eNB and SCell eNB; and, the UE controls a transmitting power for transmitting HARQ feedback information on PUCCH resource, according to the semi-static power control parameters and the TPC. A method includes computing the corresponding, maximum transmitting power available under the current condition and properly configuring the transmitting power at the terminal device by comprehensive analysis of the power control parameters received from a plurality of eNBs so as to optimize the performances of the communication system.