Not only high strength and high wear resistance were required for ductile iron crankshaft castings with oil channel, but also high air tightness was required. The possible hole defects in crankshaft was easy to become the leakage channel of gasoline, so the hole defects must be avoided. The cause of formation of hole defects in crankshaft casting is analyzed, such as shrinkage porosity and subcutaneous pores, and probes into the formation mechanism of hole defects in crankshaft oil channel edge of automobile nodular cast iron. The production practice has proved the effectiveness of the optimization measures.