Abstract: In-mold labeling processing adds a label on the part surface in mold.It is a new technology and is becoming more and more popular.It affords the mold designer far greater latitude in the design of graphics, part shape and the use of multiple molded components in a single molded unit. But the CAE technology in injection molding can’t meet the need of the new processing.There is no suitable mathematical model established for the processing.The cavity surface is always meshed in planar triangular elements. Supposing that the label and part are two plates in perfect contact,unsteady heat transfer model was established under first dissymmetry boundary for each plate.This heat transfer model was used in cooling analysis for mathematical modeling of in-mold labeling for cooling analysis in injection molding.