In order to reveal the interaction mechanism between polyamine inhibitor PF-UHIB and bentonite，the interaction between polyamine PF-UHIB and sodium bentonite（Na-MMT）was investigated by FTIR，XRD，SEM and Zeta potential analysis. Molecular dynamics simulation of this interaction was developed by Material Studio software. The results showed that PF-UHIB could dissociated ammonium ions，which adsorbed on the interlays and surface of clay through electrostatic interaction and pushed out hydrone from clay interlays. The hydrophobic group of PF-UHIB prevented the contaction between hydrone and clay. Meanwhile，hydrogen bonds formed between polyamine molecules and siloxane groups in tetrahedral layers of the clay，which prevent PF-UHIB from entering into clay sheet. In this way，the hydration and swelling of the clay were inhibited effectively.The adsorption of PF-UHIB on the clay had an adsorption equilibrium state with Zeta potential of the clay was about -20 mV，and the dispersion of clay was inhibited availably. The SEM photos displayed that the bond of clay particles was tighter，and the dispersion degree of clay reduced obviously.