A method for implementing user registration based on Diameter network protocol, comprising the following steps of: after receiving a network attaching request of a user, a requesting node sending an Update Location Request message to a Home Subscriber Server of the user, wherein the message includes information indicating whether it is necessary to download user subscription data, and also includes information indicating capability of the requesting node when the downloading is necessary (410, 502); and upon receiving the Update Location Request message, the HSS of the user returning an Update Location Ack message to the requesting node if a check of the user is passed; if the Update Location Request message indicates that it is necessary to download user subscription data, the HSS determining the user subscription data supported by the requesting node according to the information indicating the capability of the requesting node, and including the user subscription data in the Update Location Ack message to be returned to the requesting node (420, 503); characterised in that: the information indicating capability of the requesting node refers to: whether the Update Location Request message carries capability information of the requesting node; when the requesting node does not support all user subscription data, the Update Location Request message transmitted to the HSS by the requesting node carries the capability information of the requesting node; when the requesting node supports all user subscription data, the Update Location Request message transmitted to the HSS by the requesting node does not carry the capability information of the requesting node. after receiving a network attaching request of a user, a requesting node sending an Update Location Request message to a Home Subscriber Server of the user, wherein the message includes information indicating whether it is necessary to download user subscription data, and also includes information indicating capability of the requesting node when the downloading is necessary (410, 502); and upon receiving the Update Location Request message, the HSS of the user returning an Update Location Ack message to the requesting node if a check of the user is passed; if the Update Location Request message indicates that it is necessary to download user subscription data, the HSS determining the user subscription data supported by the requesting node according to the information indicating the capability of the requesting node, and including the user subscription data in the Update Location Ack message to be returned to the requesting node (420, 503); characterised in that: the information indicating capability of the requesting node refers to: whether the Update Location Request message carries capability information of the requesting node; when the requesting node does not support all user subscription data, the Update Location Request message transmitted to the HSS by the requesting node carries the capability information of the requesting node; when the requesting node supports all user subscription data, the Update Location Request message transmitted to the HSS by the requesting node does not carry the capability information of the requesting node. the information indicating capability of the requesting node refers to: whether the Update Location Request message carries capability information of the requesting node; when the requesting node does not support all user subscription data, the Update Location Request message transmitted to the HSS by the requesting node carries the capability information of the requesting node; when the requesting node supports all user subscription data, the Update Location Request message transmitted to the HSS by the requesting node does not carry the capability information of the requesting node. whether the Update Location Request message carries capability information of the requesting node; when the requesting node does not support all user subscription data, the Update Location Request message transmitted to the HSS by the requesting node carries the capability information of the requesting node; when the requesting node supports all user subscription data, the Update Location Request message transmitted to the HSS by the requesting node does not carry the capability information of the requesting node.