Abstract: A quality assurance technique for ensuring mechanical properties of casts is discussed. The technique is performed by many steps including: rapid chemical analysis to get the components of melted iron,steel,aluminum or copper and mixing and melting programs adjustment according to the results;rapid metallographic analysis to get information of the casts then send to the moulding programs to avoid the disqualified iron melt,aluminum melt,aluminum melt or copper melt moulding into casts. The quality assurance technique ensures the wanted chemical components and metallographic information,so the mechanical properties and the quality of the casts are well assured. The technique has been used on the practices of making irons and steels,the result shows that the passing percent of mechanical property of single cast has reached 98% after using the technique.