Abstract: The piercing principle of 2-roll cross-rolling piercer and its application range are discussed. It is pointed out that it is not a purpose for a rational technology of 2-roll cross-rolling piercer to try best to restrict cavities or eliminate them. By comparison of roll types, both 2-barrel -roll cross rolling piercer and 2-cone -roll cross rolling piercer can meet the requirements of direct piercing of CC billets and tube making of high alloys （including some hard reformed ones）.