The invention discloses a micro-fluidic chip as well as a modifying method and application thereof to the detection of quantity of food bacteria. The modifying method comprises the following steps: (1) modifying a -CH3 group on the inner surface of a micro-fluidic pipe on the micro-fluidic chip into a -OH group; (2) after the completion of reaction in the step (1), introducing an amino silane reagent into the micro-fluidic pipe for aminosilane reaction; (3) after drying, introducing a dendritic macromolecule of which the surface is modified by -COOH into the micro-fluidic pipe for coupling reaction; (4) after the completion of reaction in the step (3), introducing an adaptor solution which has the specific recognition performance for to-be-detected bacteria and of which a 5-terminal is modified by amino into the micro-fluidic pipe, so that an adaptor is grafted onto the surface of the dendritic macromolecule. The micro-fluidic chip as well as the modifying method and the application thereof disclosed by the invention have the benefits that the micro-fluidic chip is modified, so that the quantity of the food bacteria can be quickly detected, and the detection efficiency is improved;a whole detection environment is independent and safe, so that the cross contamination is prevented.