Abstract: The three design faults staying with the piercer plug bar support system of the Φ177 mm PQF mill plant are described here in the paper.And accordingly, modification measures as follows are worked out.Such measures include:getting out the height-adjusting pull-rod from the plug bar support system, replacing the support roller seat block with a fixed U-grooved roller seat, changing the existing support roller bearing mounting type to an insert-in-the support roller type, and changing the sizes of both the support roller and the bearing.Such modifications aim at eliminating operation faults and cutting down the production costs as well.