Abstract: The Assel tube mill imported from Mannesmann Demag Meer by Daye Steel Works is the first one with hydraulic quick-opening system, which has unique features in structure and a much wider product range compared with Transval three-roll tube mill. The paper describes the tube mill’s structure, Performances, features, operation procedures as well as Process-programming etc., The mill is valuable as reference for technical modification of the φ76mm seamless steel tube mills employed in this country.