When liquid carbon dioxide goes through a adjutage, dry ice will lock it with the depressing pressure of liquid carbon dioxide. For this reason, the authors put forward a new design using a capillary to settle the actual question. They study the mass flux characteristic of liquid carbon dioxide in a capillary the length, inner diameter and input pressure of which are different. On this condition, it has been regressed experiential expression of liquid carbon dioxide's mass flux characteristic in a capillary, and it has a value of engineering field to some extent.