Abstract: In view of the problem of high surface longitudinal cracks index of small beam blank in Ma'anshan Iron and Steel Co. Ltd., the longitudinal cracks after rolling and the composition of mold powder were analyzed, and the flow and temperature distribution in the mold were simulated. The results indicate that, the main causes of longitudinal cracks of the small beam blank are mold powder properties altered during casting, and uneven flow and heat transfer of the beam blank tubular mold. According to the characteristics of longitudinal cracks of small beam blank, the protection and pouring process of small beam blank were developed, and the tubular mold were redesigned which made heat transfer homogeneously. The surface longitudinal crack index is reduced from above 100 mm/m to less than 30 mm/m. The grinding ratio after rolling is significantly reduced from about 4% to below 1% after process optimization.