A method for transmitting uplink response signals, base station, mobile station and communication system, includes judging whether to use a downlink secondary component carrier to transmit data to a mobile station; if the judging result is positive, allocating resources according to the number of transmission blocks for transmitting the downlink data in the secondary component carrier, accordingly the mobile station is able to use the resources corresponding to a preconfigured primary component carrier and the resources allocated to the secondary component carrier to select uplink resources for transmitting response signals.