For the cracking in the panel mold of steel Stavax ESR washing machine, the fracture failure in the mold was studied by fracture scanning electron microscopy and micro-zone energy spectrum analysis, and the matrix structure was detected by metallographic microscope. The internal cause of mold cracking was residual undissolved granular and flaky carbide along the grain boundary in the organization, the sharp decrease of material strength, and the remarkable increase of brittleness. In the hot-rolling process of mold, mesh carbide was separated out along the grain boundary, and undissolved granular and flaky carbide were formed by the solid solution and aggregation during the heat treatment and heating process. Therefore, the thermal stress of heating process and the microstructural stress of quenching process resulted in internal cracks around the undissolved granular and flaky carbides. Furthermore, the cracks with intergranular cracking characteristics were exposed in the machining process of mold cooling water hole, and the work stress produced by the load of mold promoted a further crack initiation and propagation.