Embodiments of the present invention disclose a subscription information download method, a related device, and a system. The method includes: receiving, by a first network device, a first request, where the first request is sent by a terminal after connecting to and attaching to a first network when the terminal has no effective profile, and is used to request to establish a network connection for downloading a profile; establishing, by the first network device, the network connection used for downloading the profile; and returning a response message for the first request to the terminal device, to inform the terminal device that the network connection has been successfully established.