The embodiment of the invention provides a backlight module and a display device, and relates to the technical field of liquid crystal display. The uncontrollable color cast problem caused by a traditional net-point light guide plate can be solved, and even color cast of the light guide plate can be guaranteed. The backlight module comprises a light guide plate and a backlight lamp arranged on one side of the light guide plate; the light guide plate comprises a light guide body and a transparent material layer arranged on the light-output side surface of the light guide body; the light guide body is different from the transparent material layer in refractive index, and the thickness of the transparent material layer is gradually reduced from one side close to the backlight lamp to one side far away from the backlight lamp. The backlight module and the display device are used for a liquid crystal display device.