Abstract: Chitosan is a widespread natural cationic polysaccharide with characteristics of safty，nontoxicity，excellent biocompatibility and biodegradability. Chitosan has potential applications in non-viral gene delivery，while it is restricted by its poor solubility，weak targeting and low transfection efficiency. In response to these shortcomings，a series of chitosan derivatives for gene carriers have been investigated through modification of chitosan. This review presents the status and development of modified chitosan derivatives as non-viral gene deliveries with emphasis on the cytotoxicity and transfection efficiency.