A multicast service transmission method and a device, the method comprising determining, by a core network device, a coverage requirement of a to-be-transmitted multicast service, transmitting, by the core network device, the coverage requirement to an access network device, where the coverage requirement is used to determine a transmission parameter used to transmit the multicast service to a terminal device, receiving, by the access network device, the coverage requirement, determining, by the access network device according to the coverage requirement, the transmission parameter, and transmitting, by the access network device, the multicast service to the terminal device according to the transmission parameter.