A method for implementing relay station downlink retransmission and a relay station are disclosed by the present invention. According to the situation of the least available radio resource number for retransmission data on a retransmission sub-frame, the relay station of the present invention performs corresponding physical layer processing in advance for the data to be retransmitted until the OFDM signal is generated, and retransmits the OFDM signal on the retransmission sub-frame. By the method of the present invention, the problem is resolved efficiently that the relay station cooperative communication cannot be performed normally due to the change of the radio resource number during downlink data retransmission, so that the normal implementation of the relay station downlink cooperative communication is ensured; furthermore, the method of the present invention does not induce any extra overhead and time delay, needs no signaling control, can be easily implemented, reduces the system complexity, ensures the flexibility of sub-frame configuration, thereby improving service quality and resource utilization rate.