A packet transmission method, device, and system are disclosed, and pertain to the field of network technologies. The system includes a first network device in a VPLS network and a second network device in a VPWS network. The first network device determines, based on a destination address carried in a received first packet, a virtual port corresponding to the destination address in a VPLS instance of the first network device, and sends the first packet to a second VPWS instance in the second network device based on the virtual port, where the virtual port is used to indicate a first VPWS instance in the first network device, and the second VPWS instance and the first VPWS instance are VPWS instances used to bear a same service.