An access gateway establishes a link with at least one terminal device via a user interface module, and obtains a cloud storage service list from a backend server. The access gateway selects one cloud storage service from the cloud storage service list, and authenticates one cloud storage service provider server corresponding to the selected cloud storage service to obtain a backend uniform resource locator (URL). The access gateway downloads backend software from the one cloud storage service provider server according to the backend URL, and installs the backend software. The access gateway provides cloud storage service from the one cloud storage service provider server to the at least one terminal device according to the installed backend software.