The invention provides an efficient carbon dioxide snow spray gun. The efficient carbon dioxide snow spray gun comprises a casing, a carbon dioxide expansion cavity, a compressed air cavity, a mixing nozzle arranged at the front end of the casing as well as a carbon dioxide inlet and a compressed air inlet which are arranged at the rear end of the casing, wherein the carbon dioxide expansion cavity and the compressed air cavity are formed in the casing and mutually communicate. The efficient carbon dioxide snow spray gun is characterized in that a spiral slot is formed in the inner wall of the carbon dioxide expansion cavity. After the spiral slot is formed in the inner wall of the carbon dioxide expansion cavity, when sent high-pressure carbon dioxide gas is rapidly decompressed in the carbon dioxide expansion cavity and has phase change, the phase change route of carbon dioxide is effectively prolonged due to arrangement of the spiral slot, more carbon dioxide has phase change, small-particle solids are formed, the phase change conversion rate of carbon dioxide is increased, and the efficient cleaning requirement is met. The efficient carbon dioxide snow spray gun is simple in structure, convenient to use and remarkable in cleaning effect.