Based on Quandt-Elser structural model of icosahedral AlPdMn quasicrystalline approximant

and by using the ab-initio computation package VASP

the electronic density of state（DOS） and the charge density of i-AlPdMn approximant were calculated.The results show that a deep pseudogap with a width of about 1 eV exists at the Fermi level in the DOS curve;the Mn d peak is widened and locates at a lower energy;the valence electrons are localized at the middle of Al—Mn

Al—Pd

Al—Al atomic pairs

which shows covalent bonding character;the bond of Al—Mn is the strongest.With the pseudogap and the covalent bonding characteristics the special physical properties of i-AlPdMn quasicrystal and approximant can be well explained.