A network sharing device communicates with a network supplier and a client, wherein the network supplier is used for sending network sharing authorization information so as to provide a shared wireless network; the client is used for sending network sharing request information so as to share the shared wireless network provided by the network supplier; a processing unit in the network sharing device comprises: an authorization information acquiring module for receiving the authorization information send from the network supplier, wherein the authorization information comprises a service set identifier and a network key of the network supplier therein; a request information acquiring module for acquiring network sharing request information sent from the client; and an authorization module for authorizing the client to share the wireless network provided by the network supplier after the request information acquiring module acquires the request information. The present invention further provides a network sharing system and a network sharing method. The network sharing device, network sharing system and network sharing method avoid network resource waste and are convenient for users to use.