The present invention provides a service access method, device, and system, and relates to the field of television services, to guarantee multicast security of a network device. The method includes: obtaining an authorized multicast address list according to program channel list information provided by a server; receiving an Internet Group Management Protocol IGMP packet request sent by a user terminal device, where the IGMP packet request carries a multicast address; verifying the multicast address in the IGMP packet request according to the multicast address list; and sending a media data stream corresponding to the verified multicast address to the user terminal device. The solutions of the present invention are suitable for realizing the security of multicast of network device.