Abstract: The chemical compositions of the die material,the fracture appearance and the micro-structure of two kinds of the failure dies in production process were analyzed and the effects of the layer temperature on the die service life also were analyzed.It shows that the chemical composition unqualified,the electric spark machining flaw and the stress concentration are the main reasons to the early failure die and that the surface layer temperature increment of the die has an extremely important influence on the distortion invalidation of the die during the forging process.Finally the measures of improving the die service life are put forward in the actual production and achieved a certain effects.