A method includes: setting up, by a first network device, a MACSec channel to a second network device according to the MACSec protocol; and sending, by the first network device, an ACP packet to the second network device by using the MACSec channel, where the ACP packet is carried in a MACSec frame, and a frame header of the MACSec frame carries identification information used to identify the ACP packet. By means of the packet transmission method, MACSec channel is set up between adjacent nodes in a self-organizing network according to the MACSec protocol, and an ACP packet is transmitted between the adjacent nodes by using the MACSec channel and processed.