Example message transmission methods and apparatus are provided. One example method includes obtaining a first correspondence by a core network device, where the first correspondence includes a correspondence between target device information and first time sensitive networking (TSN) domain information. The target device information is used to identify a target device, and the first TSN domain information is used to identify a TSN domain to which a first TSN device belongs. The core network device receives a multicast message from a second TSN device, where the multicast message includes second TSN domain information which is used to identify a TSN domain to which the second TSN device belongs. The core network device sends the multicast message to the target device when determining, based on the second TSN domain information and the first correspondence, that the second TSN device and the first TSN device belong to a same TSN domain.