In this work, the permanent magnetic field was applied to prepare gold alloy and the influences of permanent magnetic field on secondary dendrite arm spacing and precipitate of gold alloy was also discussed. The results show that the rotating magnetic field remarkably refined the microstructure and reduced secondary dendrite arm space of gold alloy. However, a too high rotating speed can increase the skin effect of the molten metal and lower the magnetic flux density of the centre, thereby increasing secondary dendrite arm space. The area fractions of α2 can be increased by rotating magnetic field. At 300r/min, the gold alloy had the highest area fractions of α2, which was 59.4% higher than without permanent magnetic field.