The semi-continuous casting ZL205 Aaluminum alloy ingot was treated by different ultrasonic treatment at 720℃.Three groups of experiments were designed by adjusting ultrasonic action time（2、4、6、8、10 min）and ultrasonic power（0、100、120、140、160、180、200 W）to analyze effect mechanism of different ultrasonic field parameters on the solidification microstructure of ingots and to determine the optimal ultrasonic process parameters.The results show that the ultrasonic effect on the semi-continuous casting ZL205 Aaluminum alloy melt can promote the homogeneity of the eutectic structure distribution

significantly refining the grains and improving the comprehensive mechanical properties of the ingot.Ultrasonic energy can refine effectively intermetallic compounds

improving the formation and uniform distribution of intermetallic compounds

thereby increasing the nucleation rate

which is responsible for significantly improving the quality of the ingot.With a given ultrasonic power

the optimal ultrasonic action time is 10 min

and with a fixed ultrasonic action time

the optimal ultrasonic power is 160 W.The optimal ultrasonic process parameters can be obtained by three groups of experiments:ultrasonic action time of 10 min and ultrasonic power of 160 W.