The present disclosure relates to congestion flow identification methods. One example method includes obtaining, by a network device, a queue length of a non-congestion flow queue, where the non-congestion flow queue includes a data packet or description information of the data packet, determining, by the network device, a target output port of a target data packet when the length of the non-congestion flow queue is greater than or equal to a first threshold, where the target data packet is a data packet waiting to enter the non-congestion flow queue or a next data packet waiting to be output from the non-congestion flow queue, and when utilization of the target output port is greater than or equal to a second threshold, determining, by the network device, that a flow corresponding to the target data packet is a congestion flow.