Aimed at the problems that the dynamic network topology and the limited link capacity lead to frequent network link congestion phenomenon in the process of updating, and the network update process is easy to cause network congestion, reducing the network update success rate, this paper proposes a softwaredefined network update strategy based on congestion avoidance. Firstly, the initial update operation sequence of each data stream is calculated by the mixed update strategy, and then a congestion link sensing algorithm is proposed to realize the potential congestion link sensing in the update process. Finally, a new algorithm based on congestion avoidance is proposed to calculate the congestion free update operation constraint according to the initial operation sequence of each data stream and the perceived potential congestion link state, and to realize the maximum congestion free update of the network. The simulation results show that compared with the existing network updating strategy, the proposed updating strategy can effectively avoid the network congestion of the softwaredefined airborne network during the network updating process and improve the success rate of network updating.