Embodiments of this application disclose a congestion control method and a related device. A Transmission Control Protocol offload engine TOE sends a congestion control notification to a central processing unit CPU, where the congestion control notification instructs the CPU to obtain a target parameter, and the target parameter is used by the CPU to generate a congestion control calculation result. The TOE obtains the congestion control calculation result returned by the CPU, where the congestion control calculation result includes a congestion control window value. The TOE sends a packet based on the congestion control window value. In this application, the TOE and the CPU implement congestion control together. When a new congestion control algorithm emerges, the new congestion control algorithm may be applied without changing a structure of the TOE. Therefore, in this application, an upgrade period of the congestion control algorithm can be shortened, and flexibility can be improved.