Magnetic Compton profiles (MCPs) of grain-oriented silicon steels with different Si content were measured by a magnetic Compton scattering (MCS) technique. The profile features of the MCP difference between high permeability grain-oriented and conventional grain-oriented steels were similar to those of the theoretical sixth band related to the 3d conduction electrons of Fe. A comparison of the calculated eddy current losses between two samples revealed that Si content affects the contribution degree of 3d conduction electrons to eddy current losses. This brief note presents the relationship between electronic structure and eddy current loss.