The invention provides a microenvironment double-response chitosan gene carrier as well as a preparation method and application thereof. The method is started from oligosaccharides of chitosan, and synthesizes macromolecular chitosan (SRCS) containing an acylhydrazone bond and a disulfide bond. The method adopts a covalent grafting method to carry out polyethyleneimine (PEI) grafting and polyethylene glycol (PEG) grafting on the SRCS, thus obtaining oxidation reduction microenvironment and acid microenvironment double-response SRCS-g-PEI-g-PEG polymer. The SRCS-g-PEI-g-PEG polymer prepared by the invention has performance of microenvironment double-response gene release control. The invention also provides the application of the SRCS-g-PEI-g-PEG polymer obtained by the method as a gene carrier in gene transfection; the SRCS-g-PEI-g-PEG polymer has good biocompatibility and high gene transfection efficiency, thus being a good carrier for gene transfection and having a wide application prospect.