The invention discloses a method for designing bidirectional-trunk mutual-transmission beamforming on the basis of network coding, comprising the following steps: receiving data sent by a user node by a relay node, and carrying out network coding; setting a beamforming weighted vector to weight a plurality of antennae; coding the data by a plurality of weighted antennae; respectively transmittingdata to the user node, wherein the beamforming weighted vector comprises a first unbiased estimator and a second unbiased estimator, and the first unbiased estimator and the second unbiased estimatorobtain a channel gain vector between the user node and each antenna of the relay node; according to the first unbiased estimator and the second unbiased estimator, setting a first adaptive weighting parameter and a second adaptive weighting parameter; and according to the first unbiased estimator, the second unbiased estimator, the first adaptive weighting parameter and the second adaptive weighting parameter, setting the beamforming weighted vector. With the method, the first adaptive weighting parameter and the second adaptive weighting parameter are introduced in to design the proper beamforming weighted vector, and the channel gain from the relay node to the user node is improved.