The invention discloses a macromolecular coupling agent for bacterial cellulose surface modification as well as a preparation method and an application thereof. In the preparation method, the macromolecular coupling agent is prepared by firstly synthesizing two kinds of macromolecular coupling agents, carrying out surface modification on bacterial celluloses and functional groups on the macromolecular coupling agents through chemical reaction in liquid disperse medium under the function of an acid catalyst, and carrying out treatments of washing and drying. By adopting modified bacterial celluloses, the macromolecular coupling agent has the advantages of mild conditions and simple and economic technology, obviously improves the hydrophobicity of the bacterial celluloses with surface modification and can remarkably enhance the compatibility of the celluloses and a polymer matrix (in particular to polylactic acid).