The invention discloses a full-automatic film pasting mechanism for a battery piece. The full-automatic film pasting mechanism comprises a bottom plate, a reflective film support, a driven wheel, a dead weight tension mechanism, a guide rail mounting plate, a mounting plate driving mechanism, a film feeding guide wheel, a film feeding mechanism assembly, an elastic pressing wheel set, a compression mechanism and a synchronous belt base plate. The reflective film support, the driven wheel, the dead weight tension mechanism and the mounting plate driving mechanism are all mounted on the bottom plate, the guide rail mounting plate is mounted on sliding blocks of a linear guide rail on the bottom plate, and the upper end of the guide rail mounting plate is connected to a synchronous belt of the mounting plate driving mechanism through the synchronous belt base plate. The film feeding guide wheel, the film feeding mechanism assembly and the elastic pressing wheel set are all mounted on the guide rail mounting plate. The full-automatic film pasting mechanism has the advantages that the full-automatic film pasting mechanism can complete film pasting work of a single battery piece and a whole battery string, intelligent releasing and stopping of solder strips are achieved through signals fed back by an in-place sensor in the film pasting process, multiple reflective film rolls can be mounted on the mechanism at the same time, and compatibility over battery pieces of various specifications is achieved.