Backlight module, display device and assembly method of backlight module

The embodiment of the invention discloses a backlight module, a display device and an assembling method of the backlight module. The backlight module comprises a back plate, a rubber frame, a light bar, an optical film and a light guide plate. The back plate comprises a bottom plate and a side wall which is formed by extending from the peripheral edge of the bottom plate to the light emitting side of the light guide plate; the rubber frame is buckled on the outer side of the back plate, the light guide plate and the optical film are located between the rubber frame and the bottom plate, and the optical film is located on the side, away from the bottom plate, of the light guide plate. The light bar is located on the light inlet side of the light guide plate and fixedly combined between the rubber frame and the side wall. The light bar comprises a circuit board and a plurality of light source areas arranged on the surface of the side, close to the side wall, of the circuit board. The circuit board and the side