The aerodynamic forces acting on a discus were measured by wind tunnel tests, and the optimization study on discus throw was carried out by using a genetic algorithm. It was found that the stalling angle is about 30°, and the higher the spin rate the smaller the stalling angle. From the optimization study, it was revealed that the spin rate on its transverse axis should be maximized, and the angle of attack should increase from the negative value to the positive value with increasing time. The absolute value of the angle of attack should be less than the stalling angle during the whole flight.