The invention discloses an MAC layer cooperative power allocation method, belonging to the field of MAC layer cooperative communication. In the case that the conditional probability is limited, the scheme of the invention performs optimized allocation on the transmission power of a source node and a relay node, and the power consumption of the system can be further reduced. From the perspective ofthe quality of network services, that is, when the outage probability is limited, an optimal total power allocation scheme is provided in consideration of the cooperation failure in actual cooperation, that is, in the case that no suitable relay node exists. The scheme of the invention is beneficial to extending the lifetime of the nodes on the basis of ensuring the required QoS.