Abstract: A method for manufacturing light guide plate mold cores to form a precise pattern on a light guide mold core to produce light guide plates for back light modules. The method includes forming a metal layer of a selected pattern by a micro lithography process that has varying heights, and plating a layer of non-electrolyzed nickel (nickel-phosphorus alloy) to form the surface of the light guide plate mold core. The mold core thus formed, has a smooth surface, a desired mold releasing property and is durable.