In this paper, the geometry influence of reflectors for infrared rapid surface heating on micro-injection molding was studied. A three-dimension ray tracing combined with transient thermal simulation was used to evaluate the thermal condition of injection mold surface. Several kinds of reflectors were applied to study the heating ability of the infrared rapid surface heating system. A commercially available optical analysis program, TracePro, was used to simulate the infrared emission to the center of mold surface. Thermal module of a structure analysis software, ANSYS, was used to study the absorption and heat transfer of the infrared heating on the mold surface. Then, Taguchi method was adopted to find the close to optimal reflector for rapid surface heating of micro-injection molding.