A group multicast method, wherein the method comprises: receiving, by a mobile network platform, an access request for a device group, wherein the access request is sent by a service layer apparatus, wherein the access request includes an identifier of the device group and request content, and wherein the device group is a group that includes a member device supporting mobile network multicast in a machine-to-machine communications M2M group and the mobile network platform is requested to create the device group; determining, by the mobile network platform, an identifier of an external group corresponding to the device group, wherein the mobile network platform stores a correspondence between the external group and the device group, and wherein the identifier of the external group is stored in a mobile network server and the external group is a group created by the mobile network server according to an instruction of the mobile network platform, wherein each member device in the external group supports mobile network multicast and the member device in the external group is the same as the member device in the device group; sending, by the mobile network platform, a mobile network multicast request to the mobile network server, wherein the mobile network multicast request carries the identifier of the external group and the request content, the mobile network multicast request is used to instruct the mobile network server to send an access command to the member device in the external group in the mobile network multicast communication manner, and the access command carries the request content, to request to access the member device in the external group; and receiving, by the mobile network platform, response information sent by the member device in the external group, aggregating the response information of member devices in the external group to generate aggregated response information, and sending the aggregated response information to the service layer apparatus. receiving, by a mobile network platform, an access request for a device group, wherein the access request is sent by a service layer apparatus, wherein the access request includes an identifier of the device group and request content, and wherein the device group is a group that includes a member device supporting mobile network multicast in a machine-to-machine communications M2M group and the mobile network platform is requested to create the device group; determining, by the mobile network platform, an identifier of an external group corresponding to the device group, wherein the mobile network platform stores a correspondence between the external group and the device group, and wherein the identifier of the external group is stored in a mobile network server and the external group is a group created by the mobile network server according to an instruction of the mobile network platform, wherein each member device in the external group supports mobile network multicast and the member device in the external group is the same as the member device in the device group; sending, by the mobile network platform, a mobile network multicast request to the mobile network server, wherein the mobile network multicast request carries the identifier of the external group and the request content, the mobile network multicast request is used to instruct the mobile network server to send an access command to the member device in the external group in the mobile network multicast communication manner, and the access command carries the request content, to request to access the member device in the external group; and receiving, by the mobile network platform, response information sent by the member device in the external group, aggregating the response information of member devices in the external group to generate aggregated response information, and sending the aggregated response information to the service layer apparatus.