The effects of the stirring current and frequency on the microstructure of the semi-solid 2A50 alloy at the central and peripheral parts of the billet were studied. Results showed that the coarse dendritic particles were the main constituent of the microstructure without electromagnetic stirring, where the length of the dendrite arm was larger than 200 μm. This type of semi-solid billet was unqualified for the semi-solid forming. With the increase in stirring current or stirring frequency, the average size of the grains located at the central and peripheral regions decreased first and then slightly increased when the stirring current and stirring frequency is over 30A and 30Hz, respecitvely; the shape factors at centeral and center parts gradually increased and then slightly decreased when the stirring current is 40A or the stirring frequency is 40 Hz; Furthermore, the uniformity of the grain size and shape at the central and peripheral parts was improved with the increase in the stirring current or the frequency. The optimal average grain size and the shape factor were able to be obtained as 75.6 μm and 0.73, respectively under the stirring current of 30A and stirring frequency of 30Hz.