A congestion control method, wherein the method is applied to a data center network, the data center network comprises a first network device and a second network device, the first network device is configured to send a data flow to the second network device, and the method comprises: receiving, by the first network device, a first message sent by the second network device, wherein the first message carries an active flow quantity, and the active flow quantity is a quantity determined by the second network device based on a data flow to which data packets received from the first network device belong; determining, by the first network device based on the active flow quantity and rated receiving bandwidth of the second network device, packet sending control information used to send the data flow to the second network device, wherein the packet sending control information indicates that: when the first network device sends the data flow to the second network device based on the packet sending control information, actual receiving bandwidth of the second network device reaches the rated receiving bandwidth; and sending, by the first network device based on the packet sending control information, the data flow to the second network device, wherein the determining, by the first network device based on the active flow quantity and rated receiving bandwidth of the second network device, packet sending control information used to send the data flow to the second network device comprises: when the active flow quantity is less than a first threshold, determining, by the first network device based on the following formula, the packet sending control information used to send the data flow to the second network device: V = C * T active _ qp wherein C is the rated receiving bandwidth of the second network device, active_qp is the active flow quantity, T is a time required for a data packet sent by the first network device to the second network device to arrive at the second network device when the network is idle, and V is a data volume of the data flow sent by the first network device to the second network device within T; and the sending, by the first network device based on the packet sending control information, the data flow to the second network device comprises: sending, by the first network device, data packets with a data volume V in the data flow to the second network device within T. receiving, by the first network device, a first message sent by the second network device, wherein the first message carries an active flow quantity, and the active flow quantity is a quantity determined by the second network device based on a data flow to which data packets received from the first network device belong; determining, by the first network device based on the active flow quantity and rated receiving bandwidth of the second network device, packet sending control information used to send the data flow to the second network device, wherein the packet sending control information indicates that: when the first network device sends the data flow to the second network device based on the packet sending control information, actual receiving bandwidth of the second network device reaches the rated receiving bandwidth; and sending, by the first network device based on the packet sending control information, the data flow to the second network device, wherein the determining, by the first network device based on the active flow quantity and rated receiving bandwidth of the second network device, packet sending control information used to send the data flow to the second network device comprises: when the active flow quantity is less than a first threshold, determining, by the first network device based on the following formula, the packet sending control information used to send the data flow to the second network device: V = C * T active _ qp wherein C is the rated receiving bandwidth of the second network device, active_qp is the active flow quantity, T is a time required for a data packet sent by the first network device to the second network device to arrive at the second network device when the network is idle, and V is a data volume of the data flow sent by the first network device to the second network device within T; and the sending, by the first network device based on the packet sending control information, the data flow to the second network device comprises: sending, by the first network device, data packets with a data volume V in the data flow to the second network device within T. when the active flow quantity is less than a first threshold, determining, by the first network device based on the following formula, the packet sending control information used to send the data flow to the second network device: V = C * T active _ qp wherein C is the rated receiving bandwidth of the second network device, active_qp is the active flow quantity, T is a time required for a data packet sent by the first network device to the second network device to arrive at the second network device when the network is idle, and V is a data volume of the data flow sent by the first network device to the second network device within T; and the sending, by the first network device based on the packet sending control information, the data flow to the second network device comprises: sending, by the first network device, data packets with a data volume V in the data flow to the second network device within T.