Abstract: The working principle and performance of BAT and BOC types compression refrigerating systems in CO₂ tobacco expanding lines were analyzed and compared, and the modification compressor in BAT type was suggested:L type compressor was replaced with a D type compressor, and 3-step compression was changed into high pressure and low pressure compression completed in one compressor.The modification of refrigerating system was:storing condensed CO₂ in a liquid container, and returning into processing vessel under pressure difference.