Injection blow molding is a method of preparing final product wherein a preform made by an injection molding is put into a bottle-shaped mold and air is blown into it while it is still hot. Development for the 1-stage blow molding for the injection blow molding process for the thick-walled PET bottles progresses to replace the functional cosmetic containers traditionally made of glasses. This thick-walled injection blow molding is designed as to have a thickness at least more than two times than that of the general containers in order to have a filling of weight and curved shape characterized in the glass materials. However, non-uniformity in the wall thickness largely appears caused by a non-uniform temperature distribution towards thickness and length directions due to thick-walled characteristics. A blow forming simulation was performed to investigate the effect of thickness distribution and to realize the uniform thickness distribution generated during elongation process of the preform of the thick-walled bottles. The temperature distribution of the preform after the injection molding was measured by using an infrared camera to investigate the temperature distribution appeared in the preform after injection molding. Viscoplastic model which is effective in describing a thermal plastic deformation was adopted for the forming simulation as a materials model. Tensile test was conducted during simulation with the three types of temperature conditions and the four types of tensile. A viscoplastic equation model was, therefore constructed based on the results from the tensile test. The simulation results suggested that the initial temperature affected the most on the formability during the blow forming. The comparison study of the cross-sectional cut with the formed product and simulation results could provide a relatively correct estimation about the shape of the product in spite of showing a little difference according to the location in the cross-sectional cut.