The invention relates to a dopamine surface modified two-dimensional nano material and a preparation method thereof. The two-dimensional nanomaterial coated by polydopamine is prepared by a one-step reaction. The problem that a conventional two-dimensional nanomaterial is poor in dispersibility in media (water and organic matters) is solved. The preparation method is the method of preparing the dopamine surface modified two-dimensional nano material. Functional groups (hydroxyl and amino) are successfully introduced to the surface of the two-dimensional nanomaterial through dopamine surface modification, so that active groups for continuous reactions are provided, and the compatibility between the media and the two-dimensional nanomaterial is enhanced. Therefore, the dopamine surface modified two-dimensional nano material provided by the invention is of significant scientific meaning, and has huge actual application value in production of a friction-resisting composite material, lubricating grease and a heat-conducting composite material.