Adsorption of cyclohexene and its dehydrogenation intermediates on the nAu/Pt(100)(n=0,1,2 means clean Pt,one monolayer and two layers of Au covered Pt surfaces,respectively.)has been investigated by self-consistent(GGA-PW91)density functional theory combined with periodic slab model.It is found that on the clean platinum,there are two kinds of favorable adsorption sites,i.e.,hollow sites and bridge sites,and the adsorption energy at the hollow site is larger than that at the bridge site.However,on the Au/Pt and 2Au/Pt surfaces,there are three kinds of adsorption sites,and the adsorption energies are alike at both the bridge site and the top site.The magnitude order of the adsorption energies is as follows:clean Pt＞Au/Pt＞2Au/Pt.The configurations of cyclohexene molecule have been distorted a little during the geometry optimizations.The lengths of C-M(M=Pt or Au,on the top layer of the slab)bonds are closely related to the corresponding adsorption energies.