The present disclosure provides a backlight module, a method for assembling the same, and a display panel. The backlight module includes: a back plate; a light bar arranged on the back plate; a light guide plate arranged on the back plate to form a gap between the light guide plate and the light bar; a film structure arranged on a light-exiting surface of the light guide plate opposite to the back plate; and a protruding part disposed in the gap, wherein opposite sides of the protruding part are in contact with at least a portion of the light guide plate and the film structure and at least a portion of the light bar respectively.