This application provides a message processing method and system, and a user plane function UPF device. The method includes: receiving user equipment (UE) authentication information sent by a session management function (SMF) device; matching a received uplink message of the UE with the UE authentication information, and if the matching succeeds, sending the uplink message that includes the UE authentication information to a first application (APP); and performing authentication by the first APP on the UE according to the UE authentication information. In the foregoing process, authentication on the UE does not need to be performed by a remote APP. This simplifies the authentication process, reduces network resource overhead, speeds up authentication on UEs, reduces the latency of UE authentication, and further increases the application switching speed.