The effects of the addition of Cu and La inhibitors on the solidification organization and phase formation behavior of Fe-6.5 wt.% Si high silicon steel were investigated. The phase composition and structure of the alloy were analysed via XRD and SEM. The magnetic performance was measured by high- and low-temperature vibration magnetometers. The results show that the microstructure of the Fe-6.5 wt.% Si alloy ingot inhibited by Cu and La can be roughly divided into 3 layers. From the bottom to the top, the phase morphology is fine crystals, columnar crystals and isoaxial crystals. The microstructure of the Fe-6.5 wt.%Si alloy is significantly refined by the addition of Cu and La inhibitors. The microstructure of the alloy with 0.05 wt.% added Cu changes from thick column crystals to slender branches, whereas that of the alloy with 0.03 wt.% added La is refined evenly. The saturation magnetization of the Cu-added alloy remains unchanged, and the coercivity increases; the addition of La results in a decrease in the saturation magnetization, whereas the coercivity increases.