A method for controlling network congestion, including overlaying an overlay network packet header on an encapsulation outer layer of a transmit packet, where the overlay network packet header includes an outer Internet Protocol (IP) header, and an explicit congestion notification (ECN) identifier of an ECN is set in the outer IP header, decapsulating the overlay network packet header for an encapsulated reply packet, where an inner congestion identifier that is based on the ECN identifier is obtained from an IP header of the decapsulated reply packet through matching, and if the decapsulated reply packet is a User Datagram Protocol (UDP) packet, forwarding the UDP packet to a preset slow channel.