Embodiments of this application disclose a collective communication method, apparatus, and system. The method includes: A first network device receives a first packet; the first network device receives at least one second packet; and the first network device sends a third packet based on the first packet and the at least one second packet. When no connection is established between the first network device and a terminal device, the first network device may aggregate and distribute collective communication packets by using a connection between the first terminal device and another terminal device.