The optimal reheating conditions to apply the thixoforging and semi-solid die casting process were investigated by changing the reheating time, the holding time, the reheating temperatures, the capacity of the induction heating system, and the adiabatic material size. In the case of solid fraction fs=50% (for semi-solid die casting), the microstructure of SSM (specimen size:d76×l90) at the condition of the first elevating time of 4 min, holding time of 1 min and holding temperature of 350˚C, the second elevating time of 3 min, holding time of 3 min and holding temperature of 575˚C, the third elevating time of 1 min, holding time of 2 min and holding temperature of 584˚C, capacity of Q=8.398KW is obtained with globular microstructure and finest. In addition, in the case of solid fraction fs=55% (for thixoforging), the SSM (specimen size:d76xl90) at the condition of the first elevating time of 4 min, holding time of 1 min and holding temperature of 350˚C, the second elevating time of 3 min, holding time of 3 min and holding temperature of 570˚C, the third elevating time of 1 min, holding time of 2 min and holding temperature of 576˚C, capacity of Q=12.04KW is obtained with the finest globular microstructure. We saw that the most important factor in a three-step reheating process is the final holding time. (Received May 22, 1998)