The invention provides a control method for a composite external field intervention solidification structure of an aluminum alloy casting. The control method comprises the following steps that molten-mode gypsum type vacuum pressurization casting is adopted, and a travelling wave magnetic field and a rotating magnetic field effect are adopted at the same time; when the temperature of melt is 630-680 DEG C, the traveling wave magnetic field is started, the electromagnetic frequency ranges from 50-80Hz, and when the temperature of the melt is reduced to 580-630 DEG C, the traveling wave magneticfield is closed, the rotating magnetic field is started, and the electromagnetic frequency is 100-120Hz; when the temperature of the melt is reduced to 550-580 DEG C, the traveling wave magnetic field and the rotating magnetic field are started, and the electromagnetic frequency is 150-250Hz. The control method has the effects of broking a dendritic crystal arm, enhancing the microscopic reinforcing, refining the crystal grains, and inhibiting the defects of loosening, and improves the mechanical property of a casting body. According to the control method, the crystal grains are refined to 20-40 microns, and the internal quality of castings is improved from level II-III to level I.