Abstract: Preparing the semi-solid billets of ZL201 alloy by low-frequency electromagnetic casting (LFEC), the effects of electromagnetic frequency, reheating temperature and holding time on their microstructures were studied. The results showed that the trend of dentritic microstructure is gradually down with increasing electromagnetic frequency from 10 Hz to 30 Hz, and a homogeneous and fine rosette/equiaxial grain microstructure can be obtained at 30 Hz. When reheating the semi-solid billets cast at 30 Hz and 630°C for 20 min, the as-cast microstructure turns gradually into homogeneous and near-spherical grains which are suitable for thixoforming.