A multicast packet processing method, wherein the method comprises: obtaining, by a first network device, a packet, wherein the packet comprises a payload; generating, by the first network device, a first multicast packet and a second multicast packet based on the packet, wherein the first multicast packet comprises a first multicast packet header and the payload, the first multicast packet header comprises first in-situ flow information telemetry information and a first multi-level flow identifier, the first multi-level flow identifier is for identifying a first forwarding path of the payload, the first forwarding path comprises a path from the first network device to a second network device, the second multicast packet comprises a second multicast packet header and the payload, the second multicast packet header comprises a second multi-level flow identifier and the first in-situ flow information telemetry information, the second multi-level flow identifier is for identifying a second forwarding path of the payload, the second forwarding path comprises a path from the first network device to a third network device, the first in-situ flow information telemetry information indicates the second network device to perform in-situ flow information telemetry on a flow to which the first multicast packet comprising the first multi-level flow identifier belongs, the first in-situ flow information telemetry information indicates the third network device to perform in-situ flow information telemetry on a flow to which the second multicast packet comprising the second multi-level flow identifier belongs, and the second network device and the third network device are next-hop network devices of the first network device; and sending, by the first network device, the first multicast packet to the second network device through the first forwarding path, and sending the second multicast packet to the third network device through the second forwarding path, wherein the method further comprises: sending, by the first network device, a first message and a second message to a network management device, wherein the first message carries the first multi-level flow identifier of the first multicast packet and first information, the first information is information determined by the first network device based on the first in-situ flow information telemetry information in the first multicast packet, the second message carries the second multi-level flow identifier of the second multicast packet and second information, and the second information is information determined by the first network device based on the first in-situ flow information telemetry information in the second multicast packet. obtaining, by a first network device, a packet, wherein the packet comprises a payload; generating, by the first network device, a first multicast packet and a second multicast packet based on the packet, wherein the first multicast packet comprises a first multicast packet header and the payload, the first multicast packet header comprises first in-situ flow information telemetry information and a first multi-level flow identifier, the first multi-level flow identifier is for identifying a first forwarding path of the payload, the first forwarding path comprises a path from the first network device to a second network device, the second multicast packet comprises a second multicast packet header and the payload, the second multicast packet header comprises a second multi-level flow identifier and the first in-situ flow information telemetry information, the second multi-level flow identifier is for identifying a second forwarding path of the payload, the second forwarding path comprises a path from the first network device to a third network device, the first in-situ flow information telemetry information indicates the second network device to perform in-situ flow information telemetry on a flow to which the first multicast packet comprising the first multi-level flow identifier belongs, the first in-situ flow information telemetry information indicates the third network device to perform in-situ flow information telemetry on a flow to which the second multicast packet comprising the second multi-level flow identifier belongs, and the second network device and the third network device are next-hop network devices of the first network device; and sending, by the first network device, the first multicast packet to the second network device through the first forwarding path, and sending the second multicast packet to the third network device through the second forwarding path, wherein the method further comprises: sending, by the first network device, a first message and a second message to a network management device, wherein the first message carries the first multi-level flow identifier of the first multicast packet and first information, the first information is information determined by the first network device based on the first in-situ flow information telemetry information in the first multicast packet, the second message carries the second multi-level flow identifier of the second multicast packet and second information, and the second information is information determined by the first network device based on the first in-situ flow information telemetry information in the second multicast packet.