Abstract: The effect of high-intensity magnetic field on the solidified microstructure of the Cu-25wt%Ag was investigated, as well as the mechanism of the solidification processes of the alloy under different magnetic conditions. It is found that both the uniform magnetic field and gradient magnetic field can affect greatly the solidified structure of the alloy, such as the changes of the size and morphology of Cu-rich dendrites. The primary Cu-rich dendrites are distributed unevenly without magnetic field and they are comparatively thick and long, and most of them are in columnar shape. When the Cu-rich dendrites are in a 12 T magnetic field, they are distributed uniformly and the primary dendrites become short and thick, and most of the dendrites are in cellular shape. When the Cu-rich dendrites are in a negative gradient magnetic field, they are distributed unevenly, and the quantity of dendrites decrease at the bottom of samples where most of the dendrites are in faceted growth and thick cellular shape. Experimental results showed that the constantly uniform magnetic field is feasibly to control the solidified structure of the Cu-Ag alloy and available to grain refining and reducing segregation.