The atomic cluster models of α-Al, η phase and large angle grain boundary of α-Al with η phase in Al-Zn-Mg-Cu alloys have been founded by a computer program. The environment-sensitive embedding energy, and the atom action energy of Zn, Mg, Cu and the atom binding energy, the fermi energy of α-Al and/or η phase have been calculated by a recursion method. The corrosion character of Al-Zn-Mg-Cu alloys has been studied according to the calculated electronic parameter. The results show that Mg and Zn elements are easy to segregate on grain boundaries, and to form η phase. The η phase on grain boundary are large then that in grain due to the segregation of Mg in the grain boundary. The calculated results indicate that the fermi energy of η phase is the highest, will be decomposed firstly in the corrosion as an anode. The alloy element Zn has the function to increase the electrode potential difference between grain boundary and grains, to deteriorate the corrosion character of alloys. The alloy element Cu can reduce the difference of Fermi energy and the potential difference between grain and grain boundary, so as to slow down the corrosion process