The invention discloses a PVC plastic film processing flattening device capable of reducing pressure in the technical field of plastic film processing equipment. The device comprises a mounting frame, a winding roller, a mounting sleeve, a flattening block and a moving rod, wherein an adjusting device is slidably mounted in an inner cavity of the mounting sleeve, the moving rod is slidably connected to the bottom end of the inner cavity of the mounting sleeve in an inserted mode, a pushing spring is fixedly installed between the moving rod and the adjusting device, and the bottom end of the moving rod is fixedly connected with the outer wall of the top of the flattening block. In the device, a moving block slides inwards, the moving block and a mounting block move upwards, the moving block is moved to a position below an upper set of check blocks, a distance between the adjusting device and the moving rod is increased, a degree of compression of the pushing spring is decreased, through automatic adjustment of the adjusting device, the pressure of the flattening block on a thin film wound on the outer wall of the winding roller is not large, the situation that due to the fact that friction force between the flattening block and the thin film is large, the thin film is difficult to wind by the winding roller is avoided, and the flattening block is also prevented from abrading the wound thin film.