The embodiment of the invention discloses a data packet processing method, and a method, a device and a system for managing network flow. A plurality of networks can be used under the condition of establishing only one transmission control protocol (TCP) connection, and the using flow of each network can be controlled. The data packet processing method comprises the following steps that a terminal acquires an aggregation flow table, wherein the aggregation flow table comprises a management policy for managing the network flow of a first network and the network flow of a second network; the terminal determines a transmission network for transmitting a first uplink data packet from the first network and the second network according to the aggregation flow table; if transmission of the first uplink data packet through the first network is determined, the terminal sends the first uplink data packet to the first network through a first network card corresponding to the first network and forwards the first uplink data packet to a gateway through the first network; if transmission of the first uplink data packet through the second network is determined, the terminal sends the first uplink data packet to the second network through a second network card corresponding to the second network and forwards the first uplink data packet to the gateway through the second network.