The effects of DC and AC magnetic fields on the interfacial microstructure betw een molten aluminium and solid iron were studied, and the intermetallics formed in the diffusion layers were also investigated by means of metallography, electr on microprobe (EPM) and x-ray diffraction (XRD). Results showed that the diffusi on layer in solid iron under DC and AC magnetic fields was thinner than that w ithout magnetic field, and the interface became irregular under AC magnetic fiel d. In the direction perpendicular to the magnetic field, DC magnetic field dampe d the diffusion between aluminium and iron; on the contrary, under AC magnetic field diffusion was enhanced; the diffusion layer in solid iron was mainly comp osed of Fe2Al5 and FeAl3 without magnetic field , while there was only Fe2Al5 under DC magnetic field, and Fe2Al5 and Fe4Al13 under AC magn etic field.