The inhibition mechanism of alkylamines that have different numbers of primary amine groups adsorbed on sodium bentonite has been investigated using isothermal adsorption, adsorption kinetics, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental analysis (EA), cation exchange capacity (CEC), thermogravimetric analysis (TGA), linear expansion experiments and rolling recovery. The saturated adsorption capacity of alkylamines on sodium bentonite decreased with the increase in the number of primary amine groups. The adsorption rate constant increases rapidly with the increase in the number of primary amine groups on the premise that they are both water-soluble and hydrophobic. A flat-lying monolayer of each alkylamine was intercalated, replacing sodium ions in the interlayer and becoming firmly embedded in the interlayer space of sodium bentonite between the primary amine groups and silicon-oxygen tetrahedra. As a result, the water molecules present in the clay interlayer space were expelled, and the interlayer space of the clay decreased to the maximum extent. The inhibition performance of alkylamines on bentonite clearly increases with the increasing of number of primary amine groups. Therefore, a mixture of alkylamines with multiple primary amine groups is a promising intercalating inhibitor that can be used along with water-based drilling fluids has broad application prospects.