The blade cylinder root is a key component connecting the blade and pitch bearing of a wind turbine and is 20% of the blade’s manufacturing cost. Blade cylinder roots are manufactured using the open die forging method with steel alloy. However the blade cylinder root for 750 KW class wind turbine is manufactured using AA5083 cast material to reduce weight. The purpose of this study is to develop a hot open die forging method, through experiment and FEA, using AA5083 material manufactured by continuous casting. The forging process was designed using the mandrel forging method. Hot compression tests were conducted to obtain flow stress of cast microstructure at different temperatures and strain rates. Control parameters of each forging process were analyzed/compared to predict adaptability of the mandrel forging process. High productivity, good internal quality, shapes, and dimension were verified by prototypes manufactured by the proposed forging process.