In hot forging process, the common failure modes of forging die are wear, fatigue fracture and plastic deformation. Normally die wear is occurred the most frequently and it influents directly to shape, dimension and surface quality of product. For this research, the hot forging process of idle gear was studied to focus on die wear. This product is forged in three steps. There are preform step, rougher step and finisher step. Height of preform shape in preform step was a parameter to study effect on die wear. Archard’s wear model in finite element modeling was used to predict die wear. The finite element modeling was verified by real hot forging process for reliable model and then it was used to determine the optimum preform height to reduce die wear. Finally the result showed that the maximum wear depth on the forging die was reduced 41.2% from original industry process.