Abstract: The aluminum profile extrusion mold cracked during service. Macroscopic observation, chemical composition analysis, hardness test, non-metallic inclusion evaluation, metallographic examination and scanning electron microscopy analysis were used to analyze the causes of mold cracking. The results show that the improper selection of electrical discharge machining process parameters resulted in a thick white layer on the surface of the mold cavity, accompanied by microcracks, which extended to the heat affected zone, destroyed the material continuity and reduced the fatigue resistance of the mold. During the machining process, there was stress concentration at the tip. Under the action of extrusion pressure and thermal stress, cracks continuously initiated and expanded, ultimately led to mold cracking.