The invention relates to a relay code construction method for a cooperative communication system, which comprises the following steps of: determining an optimal convolutional code according to the number of source nodes and the number of input links of a destination node in the cooperative communication system and a system decoding requirement; and reversely determining a code construction scheme of a relay node in the cooperative communication system through the optimal convolutional code, and constructing a relay code. By the method, the problem of coding the relay node in the cooperative communication system is solved; and for the given cooperative communication system, the optimal code construction scheme of the relay node is determined through the optimal convolutional code, so that the given cooperative communication system achieves optimal performance.