In micro injection molding,the convective heat transfer behavior between the polymer melt and the wall of micro mold cavity is different from the conventional injection molding,the convective heat transfer coefficient has changed.With application of micro mold and temperature transducer,the mold temperature distribution of polypropylene(PP),acrylonitrile-butadiene-styrene(ABS) and two kinds of polyoxymethylene(POM) melt filling the micro-cavity with different injection speed,cavity thickness of 0.510 mm and 0.420 mm,surface roughness of 0.062 μm,0.393 μm and 0.695 μm was experimentally measured.Then the convective heat transfer coefficient was calculated.The results indicate that,the convective heat transfer coefficient is closely related to the thermo-physical properties of polymer materials,thermal properties of materials with high values has a higher convective heat transfer coefficient.At the same time,it is increased obviously with the increase of injection speed,surface roughness of the cavity and the decrease of the thickness.