Main Shaft is one of the key components to connect between Rotor hub and Gear box in wind turbine. The mechanical components for wind turbine is most being manufactured with hot open die forging. The purpose of this study is to develop the manufacture process of Hollow Main Shaft by open die forging. In case of the open die forging for large forged part, pass schedule of manufacture process is most important because it can affect final dimensions of product. In this paper, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The measured flow stress dates were used to simulate the upsetting, piercing, pipe forging and final flange upsetting process of cast ingot using the practical material properties. Also the mechanical properties after forging of Hollow Main Shaft were investigated from the experiment. From the results, the prototypes of Hollow Main Shaft were manufactured based on analyzed results, productivity was stable, mechanical properties was increased and product dimension was optimized with suggested process. With FE-Analysis and prototype, the advantages of new method (hollow type) such as material utilization, mechanical properties and production cost were verified.