In the process of riveting an MB15 forging die, cracks were discovered emerging along the longitudinaldirection and near the riveting hole. Through fracture analysis, microscopic observation, energy spectrum analysis,metallographic examination, and hardness test, the properties and causes of the cracks are discussed. The results indicatethat the cracking type is intergranular brittle cracking, occurring during the forging stage. Furthermore, the recrystallizationat the crack site is found to be incomplete, which is attributed to the low deformation temperature.