Abstract: Analyzed are the effects by relevant alloy elements on structures and properties of the nodular iron. And based on the analysis result, contents of the elements are adjusted, and enhanced-cooling operation is performed during the solidification process, which leads to the success in making heavy and large-section piercer guide disc with the said pearlitic nodular iron with hardness greater than 300 HB. And the wedge-shaped sample block for heat analysis is of needle-like bainitic structure. And the guide disc as made in the nodular iron is in compact structure, and free of any defect of shrinkage pipe or shrinkage porosity. Thanks to employment of the guide disc, the Ф340 mm MPM is capable of meeting the need for producing quality tubes like the 35CrMo tube for gas vessel service.