An embodiment of the invention provides a unified user identification generation method, device and system. The method comprises the following steps: unified application identifications distributed inadvance for applications can be searched based on application identifications via a service platform, and unified user identifications for users can be generated according to the unified applicationidentifications and user identifications. If two applications are the same in unified application identification and the user identifications are the same in corresponding associated information, thesame unified user identification is distributed for the users via the service platform; if the two applications are different in unified application identification, different unified user identifications are distributed for the users via the service platform even if the user identifications are the same in corresponding associated information, the unified user identifications are generated in sucha way, and the same users in different applications can be identified via a terminal device according to the unified user identifications; data sharing, data isolation and smooth data migration amongapplications can be realized in a flexible manner.