Abstract: The thermodynamic stability, surface energy and value of electronic work function of different crystal planes of intermetallic compounds (IMCs) in an extremely narrow weld with aluminum to steel in electromagnetic pulse welding are calculated using the first principle. Combined with scanning electron microscopy (SEM), X-ray diffraction (XRD), and other testing methods of the interface microscopic morphology, the possible presence of IMCs in the weld seam and its influence on the corrosion property of the interface are analyzed. The results show that the results of first-principle calculation are basically consistent with the experimental data, and the calculated formation energy and binding energy of Al-Fe IMCs are both negative and meet the thermodynamically stable structure, it's the strength of the formation ability as follows Fe₂Al₅, FeAl, FeAl₃, Fe₃Al and FeAl₂, and its stability is as follows, Fe₂Al₅, Fe₃Al, FeAl, FeAl₃ and FeAl₂, where the forming energy of Fe₂Al₅ is −9.379 eV/atom, and the binding energy is −13.612 eV/atom, which is the most stable phase in the weld. The corrosion resistance from weak to strong corresponding to the value of electronic work function is as follows Al, FeAl₂, FeAl_3, Fe₂Al₅, FeAl and Fe₃Al; energy dispersive spectroscope (EDS) analysis shows that Fe₂Al₅, FeAl₃ and small amounts of FeAl₂ exist in the weld, there are FeAl in elliptic ring weld, and Fe₃Al in straight weld. The value of electronic work function of weld FeAl₃ is small, which acts as the anode in the salt spray corrosion medium and is easy to be corroded. With the increase of the corrosion period, the main phase of the weld Fe₂Al₅ acts as the anode for rapid corrosion expansion from straight weld to elliptic ring weld, until the whole weld failure. The results provide data reference for controlling the morphology, connection mechanism and corrosion resistance of intermetallic compound in electromagnetic pulse welding with steel to aluminum.