A message transmission method and an apparatus are provided. In the message transmission method, a first network device receives a first request message from a second network device, where the first request message is used to request a context of a terminal device, the first request message includes first indication information, the first indication information indicates that the terminal device has initiated an SDT procedure in an RRC inactive state, and the first network device has stored the context of the terminal device; and if an amount of to-be-transmitted data in SDT of the terminal device is greater than or equal to a data amount threshold, the first network device sends an RRC release message to the second network device, where the RRC release message indicates the terminal device to terminate the SDT procedure and keep in the RRC inactive state.