A flow control method includes: when congestion is detected, determining, by a first switching device, a key flow from a plurality of data flows; generating a back pressure message including a flow attribute value of the key flow; sending the back pressure message to an upstream device of the key flow; and pausing, by the upstream device of the key flow, sending of the key flow, where the back pressure message has no impact on sending of another data flow other than the key flow by the upstream device of the key flow. The present disclosure further provides a switching device that can implement the flow control method.