A system and a method for evaluating transmission performance related to a network node, and a related device are disclosed. The system includes a network node and a control node. The network node is configured to obtain a test packet, and process the test packet by using a virtual switch, to generate a mirrored packet corresponding to the test packet. The mirrored packet carries a generation timestamp and generation location information. The control node is configured to receive the mirrored packet from the network node, to evaluate, based on the mirrored packet, transmission performance of at least a part of link that is related to the network node and that is in a path. The control node obtain transmission performance of the network node in the path and the transmission performance of at least a part of link that is related to the network node.