This application provides a flow control method, including: sending, by a first device, a first data packet to a second device in a first sending mode; determining, by the first device, a network congestion status; and sending, by the first device, a second data packet to the second device in the second sending mode, where the second sending mode is a sending mode determined by the first device based on the network congestion status, and the second data packet is a data packet to be sent after the first data packet.