Abstract: The dense pitting and water ripple defects in the polishing surface of Stavax ESR steel plastic mold were presented during the processing. The defect reasons of the dense pitting and water ripple were analyzed by methods of chemical composition analysis, hardness test, non-metallic inclusions testing and metallographic inspection. The results show that too high temperature led to coarse grain in the process of heating treatment, and the superheated tissue brought high quenching stress. At the same time, the large strip of lath-shaped martensitic beam led to the wedge crack on the surface of the mold. Wedge crack on the surface formed folding crack due to the redistribution of stress on the surface and the elastic deformation. Finally, the mold surface produced the defects of dense pitting and water ripple.