Due to its excellent mechanical strength and tunable structure, nanocellulose is widely employed for material modification to enhance mechanical and electrical properties. This study establishes models for pure cellulose, nanocellulose-modified cellulose, and cationically modified nanocellulose, analyzing the thermal stability of cellulose insulation paper. Through molecular dynamics simulations, comparisons were made between cohesive energy density, solubility parameter, free volume fraction, number of hydrogen bonds, and glass transition temperature before and after modification. The results indicate that both nanocellulose (NFC) and cationically modified nanocellulose (CNFC) enhance the molecular interactions between cellulose molecules, with CNFC exhibiting superior compatibility with cellulose. The doping of NFC and CNFC increases the glass transition temperature of cellulose, thereby enhancing the thermal resistance of cellulose insulation paper.