Abstract: Ferrite ductile iron casting was prepared by sand moulding process. The inhibition effect of Sb on chunky graphite in the center of ductile iron casting with different Si contents was compared. The effect of wall thickness of the castings with same Si content on the eutectic solidification time in the center, tensile strength, yield strength, elongation and low temperature impact property at -40 ℃ was analyzed. The results show that tiny addition of Sb had obvious inhibition effect on the chunky graphite. When the Si content was 1.8wt%-2.0wt% or 2.0wt%-2.2wt%, adding 0.005wt% or 0.008wt% Sb could completely inhibit the formation of chunky graphite and improve the mechanical properties significantly, especially the toughness. With the same Sb content, the larger the wall thickness was, the longer the eutectic solidification time was, and the lower the comprehensive mechanical properties were.