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为了从微观角度探究物理改性和化学改性提升热稳定纸抗热老化性能的机制，对纤维素改性相关的几种模型分子、热稳定剂、小分子酸、水分子和氧气进行了量子化学计算，获取了相关分子的最高占用轨道(highest occupied molecular orbital ， HOMO)能量、最低未占用轨道(lowest unoccupied molecular orbital，LUMO)能量及3种β-D-吡喃葡萄糖分子的 Mulliken 布局分布。通过反应分子间的前线轨道能隙和亲电亲核反应位点来考察不同分子间的反应活性及活性点。结果表明：热稳定纸中胺基热稳定剂先与水分子、小分子酸和氧气这些老化因子反应，从而保护了纤维素链；化学改性使得纤维素的抗氧化性能有小幅提升，但化学稳定性却被降低，由于变压器运行温度远小于起始分解温度，热解难以进行；热稳定纸的亲水性差使得纸中水分含量少，加上有机酸的消耗，纤维素水解反应进行缓慢，这在热老化实验中纸的聚合度下降较少上得到了印证。“,”In order to shed some light on the mechanism of anti-thermal ageing performance improvement of physically and chemically modification in thermally upgraded insulation paper from microscopic scale ,several modeling molecules, thermal agents,small molecule acids,water molecule and oxygen molecule were computed with quantum chemistry method to get the information about HOMO and LUMO energy and Mulliken population distribution of threeβ-D-glucopyranose molecules. The reactivity of those molecules and the active sites were investigated by energy gaps between frontier orbitals, electrophilic reaction sites and necleophilic reaction sites respectively. The results show that the cellulose molecules are protected by reaction between thermal agents and small molecule acids,water and oxygen in thermally upgraded insulation paper. Moreover, the anti-oxidation performance of chemically modified paper is improved slightly whereas the chemical stability decrease, which may lead to thermal decomposition.Actually, pyrolysis is difficult to happen due to transformer operation temperature is much lower than the initial decomposition temperature of chemically modified cellulose. As to depolymerization process in cellulose hydrolysis, the rate will be retarded by depletion of water and acids when comparison with kraft insulation paper.