The present invention provides a flow network-based return path planning method in a millimeter wave network, relating to the technical field of communications. An undirected multi-graph of a millimeter wave return network is built; the undirected multi-graph is converted into a directed multi-graph; the directed multi-graph is converted into a directed simple graph; a flow network graph is built based on the directed simple graph; a minimum cost maximum flow in the flow network graph is calculated by using a Push-Relabel algorithm; and an actual return work timeslot number of each return link is determined by using the minimum cost maximum flow obtained through calculation. The network return data amount is maximized, and further, the return energy consumption of the whole network is minimized, so that the throughput of the densely distributed millimeter wave network is maximized, further, the return path of minimum energy is planned, the network energy consumption is saved, the millimeter wave micro-base station in the network can return services through multiple paths to multiple gateways, the implementation process is simple, and the method can be applied to a single gateway or multi-gateway scene.