Abstract: Subcarrier power allocation in broadband orthogonal frequency division multiplexing（OFDM） relaying system is addressed for the nonregenerative and regenerative relaying mode. Firstly, based on the two-hop nonregenerative relaying system, an equivalent channel gain model for the two-hop regenerative relaying system is induced. Afterwards, the overall transmit power is allocated to the subcarrier pairs using water-filling approach. Finally, the above conclusions are generalized to the multi-hop relaying system. Simulation shows that the proposed power allocation algorithm can achieve a higher system capacity than both the direct transmission system and uniform power allocation scheme, and the multi-hop relaying system can efficiently enlarge the coverage.