In recent years, there is increasing demand of esthetic design and complex function in aerospace, automobile and die/mold industry, which brings into limelight high-precision, high-efficient machining of sculptured surface. This paper deals with the establishment of the optimal tool path on free form surface in high speed ball end milling. Ball end milling is widely used for free form surface die and mold. In this machining, the cutting direction was changed with tool path. The cutting characteristics, such as cutting force and surface form are varied according to the variation of cutting directions. In this paper, the optimal tool path with down cutting in free form surface cutting is suggested.