An investigation is made of a multi-antenna half-duplex relay covert communication system based on decoding and forwarding relay.By using a source node equipped with multiple antennas, the Willie detection is disrupted in two stages through transmission schemes of zero forcing beamforming (ZFB) and randomized selection jamming (RSJ), respectively, so as to protect the transmission of covert information. Firstly, the optimal detection threshold and minimum detection error probability of Willie in two stages are to be derived. Secondly, based on the constraint of average minimum detection error probability, the transmission power of the source node in the first stage and the forwarding power of the relay node in the second stage are derived, analyzed, and optimized, thus obtaining the maximum effective covert rate of each stage. Finally, based on the steganographic performance metrics of each stage, the total transmission interruption probability and the total maximum effective steganographic rate of the system can be derived. The experimental results show that when the number of antennas is no less than 3, the total transmission interruption probability of the system decreases with the increase in the number of antennas, and the total maximum effective steganographic rate of the system is the same as that of the second stage.