Abstract: Described in the paper are the main aspects concerning the modification of the Φ90 mm piercing mill as located in a steel pipe plant in Yangzhou, covering the expansion bushing of the in-mill steadier roller, roll stand bearing lubrication passage, the in-mill steadier roller proper, the roll cradle adjustment and the lateral-pressing device. Thanks to the modification of the mill, it is expected to save the annual maintenance costs by 156 hours and RMB 80 000 yuan.