The performance of insulating paper cellulose is an important factor affecting the normal operation of electric power equipment. This paper uses molecular dynamics methods to establish pure cellulose, hBN‐modified cellulose, 3‐aminopropyltriethoxysilane (KH550), 3‐glyoxypropyltrimethoxysilane (KH560), and 3‐methylpropoxypropyltris (KH570) grafted with hBN modified cellulose models. The effect of cohesive energy density (CED), thermal conductivity (TC), mean square displacement (MSD), free volume, glass transition temperature (Tg), and mechanical properties on the thermomechanical properties of cellulose are investigated and compared. The results indicate that all three silane coupling agents can enhance TC, thermal stability, and mechanical properties of the cellulose models. Among them, KH550 is the best grafting method for hBN/cellulose system as KH550 graft not only significantly enhances TC by 114.29% and Tg by 23.88% but also significantly strengthens the toughness and resistance to deformation of cellulose by over 50%.