Biaxially oriented Poly (ethylene terephthalate) film is excellent in heat-resistance and transparency, which is utilized in technical and packaging application. Heat resistance, mechanical strength, or dimensional stability is achieved by the use of biaxial orientation method, which is characterized in machine-directional and transverse-directional stretching under specific temperature. It is well known that difference of the amount of heat, temperature profile, draw ratio and strain rate in stretching process improve the film properties. Generally, the temperature of stretching process is set on a little higher than glass transition point, in order to avoid the deterioration of thickness homogeneity caused by overheating. In this work, the authors studied the new biaxial stretching process at high-temperature condition near melting point of PET. Generally it is difficult to stretch PET film at high-temperature near melting point, because tensile stress decreases during stretching process. However, PET film stretched at such high temperature can be obtained by undergoing heat-crystallization of pre-stretching film. The PET film by near melting point stretching exhibited specifically thermal dimensional stability. The result of property and structural characterization by X-ray scattering of our new film was discussed. Moreover, we studied structural change during stretching by in-situ characterization. It clarified that there is a specific crystal construction process at near melting point that affects the thermal dimensional stability.