Disclosed are a human serum albumin-siRNA carrier system having siRNA bound to human serum albumin and a user thereof, and especially, human serum albumin-siRNA carrier system, which has a biodegradable covalent bond between human serum albumin polymer and siRNA and is stable in a living body, and a user thereof.The human serum albumin-siRNA carrier system having the biodegradable covalent bond between the human serum albumin and the siRNA exhibits high siRNA delivery efficiency to a target site in the living body. Therefore, the human serum albumin-siRNA carrier system may allow siRNA for therapy to be efficiently delivered to a target site such as cancer tissues in the living body even by being administrated in a relatively low concentration, which may result in a wide use for therapies of various diseases.