The invention discloses a boron nitride dispersant, a method for peeling a two-dimensional B3N4 nanosheet at a liquid phase and application thereof. The boron nitride dispersant comprises an aniline oligomer which can be combined with boron nitride through a physical effect to enable the boron nitride to be stably dispersed into a dispersion medium. The aniline oligomer which is easy to synthesize and has low cost is used as the boron nitride dispersant and the dispersant and the boron nitride are simply mixed in the dispersion medium, such as an organic solvent; the dispersion degree and the dispersion stability of the boron nitride, especially a boron nitride two-dimensional nano-material, in the organic solvent can be greatly improved through a physical mutual effect between the dispersant and the boron nitride; furthermore, the aniline oligomer can be used for obtaining the boron nitride nanosheet through a simple liquid-phase peeling method and a physical structure and chemical performance of the boron nitride are not damaged; and moreover, the dispersion medium which is used for dispersing the boron nitride or peeling the boron nitride nanosheet can be circularly utilized, so that the cost can be reduced, the emission of organic matters is reduced and large-scale implementation is easy to realize.