The embodiments of the present invention disclose a pre-coding method in a cooperative relay system. The pre-coding method in the cooperative relay system includes: obtaining pre-coding matrixes of local optimal sub-channels to single links of respective relay stations; and obtaining a pre-coding matrix of a synthesized optimal sub-channel according to the pre-coding matrix of each local optimal sub-channel. The embodiments of the present invention also disclose a communication apparatus and a relay apparatus. The present invention is applicable to pre-coding between a transmitter and a relay station in a cooperative relay system.