This application provides a packet control method and a network device. The method includes: detecting a packet flow causing a congestion status change; generating a congestion isolation message, where the congestion isolation message is used to change a priority of a packet in the packet flow, and the congestion isolation message includes description information of the packet flow; and sending the congestion isolation message to at least one node. According to the method, the network device, and the like provided in this application, when a congestion status changes, a packet flow that causes the congestion status change may be identified, and another node may be instructed to change a priority of a packet in the packet flow without affecting transmission of another packet flow. Therefore, a packet loss caused by congestion can be avoided, and head of line blocking caused by no congestion isolation can be avoided to a large extent, avoiding congestion diffusion.