Abstract：Cellulose insulation paper is the main component of oil-paper insulation systems in oil-immersed transformers. However, the poor thermal conductivity and thermal stability of the cellulose can lead to thermal aging. It is critical to address this issue by improving the performance of cellulose, nano-SiC modified cellulose models were established by molecular simulation, while nano-SiC composite papersheets were prepared based on the simulation results, and the effects of different contents of nano-SiC on the papersheets were investigated. Macroscopically, doping nano-SiC particles can enhance the thermal stability of cellulose, compared with the unmodified papersheet, the thermal conductivity and tensile strength of the modified papersheets are increased by 44.3% and 42.8%, respectively. The degree of polymerization of the modified papersheet decreased more slowly than that of the unmodified papersheet under accelerated thermal aging, showing that the modified papersheet has better anti-aging properties. Microscopically, with the addition of nano-SiC, the simulations showed that the mean square displacement of the cellulose decreases dramatically and the distribution of the free volume becomes difficult to disperse, which corresponds to the decrease in porosity in the experiments. As a result, this research provides a way for improving the thermal-mechanical properties of cellulose that has practical application significance.