The present invention provides a light guide plate (LGP) and a backlight module. The backlight module has a light source and a LGP. The light source generates light. The LGP has a light input side surface receiving light generated by the light source; a reflective surface reflecting the light received by the light input side surface, so as to generate a planar light; a light output surface emitting the planar light; and a light compensation side surface opposite to the light input side surface and reflecting the light from the light input side surface and the reflective surface. The light compensation side surface is provided with fluorescence powders which are excited by the light to generate compensation light, so as to adjust color of the planar light emitted from the light output surface. The LGP of the present invention is provided with the light compensation side surface which is coated with the fluorescence powders to lower the color difference in surfaces of the LGP of the unilateral side-light type backlight module, so as to carry out better visual quality and product quality.