Abstract: In this paper, the effects of 90 keV proton irradiation on chemical structure of Kapton H film are investigated. X-ray photoelectron spectroscopy (XPS) analysis results show that the low energy electron irradiation induces the break of C－N and C－O bands in Kapton H film molecular structure, the break of C＝O bands and the recombination, while, some broken bands can cross the linkage again. The number of C－N and C＝O bands decreases with increasing electron irradiation energy in Kapton H film molecular structure. The surface hardness of Kapton H film increases after irradiated by 90 keV protons due to the break of C－O bands as flexible structures, and the generation of cross linkage structures and three-dimensional reticulated structures with benzene ring as the main component.