The invention provides a decode-and-forward strategy based multi-antenna relay beam forming method which includes the steps: in the first time slot, obtaining a beam forming vector of a signal source node S, enabling the signal source node S to send signals s1 to a relay node R and a destination node D simultaneously, and enabling the relay node R and the destination node D to receive the signals s1 simultaneously; and in the second time slot, enabling the relay node R to receive and decode the signals s1, recoding information to signals s2 and sending the signals s2 to the destination node D. By the decode-and-forward strategy based multi-antenna relay beam forming method, the design that the beam forming vector of the signal source node S is obtained in the first time slot is provided, so that transmission efficiency is maximized, and channel interrupt probability is minimized; and the relay technology and the multi-antenna beam forming technology are combined together, the optimal beam forming vector is designed, and accordingly transmission efficiency and reliability can be improved, and transmitting power is saved.