Three kinds of ultrasonic radiators with plane,spherical and conical shape were designed based on ultrasonic refraction and reflection theory at liquid/solid interface to understand the effects of end-shape on microstructure of aluminum alloy. Water simulation and 7050 aluminum alloy casting test were conducted,respectively,with three kinds of ultrasonic radiators. The water simulation results reveal that maximum cavitation and acoustic streaming intensity with the smallest radiation radius can be observed with the plane ultrasonic radiator,while the larger cavitation and acoustic stream effects with a larger radiation radius can be observed with the spherical ones,and the weakest cavitation and acoustic effects with the maximum radiation radius and the fastest attenuation velocity can be described with the conical ones. The effect orders of three kinds of ultrasonic radiator on the microstructure of 7050 aluminum alloy are as follows:plane tip,spherical ones,conical ones.