2, pass adjustment is given priority to, supplemented by speed adjustment principle. When the rolling force of the pipe mill is lower than the calculated rolling force and the length of the steel pipe cannot meet the requirements. Priority should be given to reducing the pass diameter of the pipe mill until the rolling force curve is close to the calculated value and the length of the steel pipe meets the requirements. Then the rolling force curve is flattened by adjusting the speed of the pipe mill, which is the so-called pass adjustment priority principle.