The intermolecular interactions between γ-aminopropyltrianolsilane (KH5501) and TATB were theoretically studied using the density functional theory LDA/PW method and the three optimized geometries of the mixture of KH5501and TATB were obtained. By analyses of bond length and bond angles of TATB before and after mixing with KH5501, It is found that the coupling agent KH5501 changes the structure of TATB in two was: the bond length of C—NO₂ bond is shortened, and accordingly, the impact sensitivty decreases. In another side the planar structure of TATB is destroyed and accordingly, the molecular polarity of TATB is enhanced. The analyses of the frontier orbits of TATB show that, the interaction between KH5501 and TATB, make the gaps of frontier orbits become narrower, thereby the thermostability as well as the photostability of TATB is debased, and the reaction activity of TATB is enhanced. Through the comparation of the calculation results between three optimized geometries, the results indicate that the bond length of N—O bond of TATB all get longer, particularly, the Ⅳ geometry gets longest. Although the electron transfer between TATB and KH5501 occur, the Ⅳ geometry transfers largest. Meanwhile, compared with other geometries, there is the largest energy of the molecular interaction in Ⅳ geometry. For mentioned above reasons, it is concluded that the Ⅳ geometry is of the largest stability among the three geometries, and the main bonding between TATB and KH5501 in IV geometry is the hydrogen bond interactions formed between the hydrogen atom in the hydroxide of KH5501 and the oxygen atom in the nitric of TATB. It is the hydrogen bond interactions, formed between the hydrogen atom in the hydroxide of KH5501 and the oxygen atom in the nitric of TATB, that improve the binding and the interfacial properties of TATB, which is consistent with the experimental results.