Abstract: The stable geometries, the bonding energies and the activation energies are calculated for ethylene adsorption on transition metal Ni(111) and Cu(111) surfaces by using EHMO method. The results show that the C-Cbond length, 1 = 1.60Å, the perpendicular distance between the C-Cbond and the metal surface, h = 1.80Å and the bend up angle of the plane HCH, θ=30° for the Ni adsorption) and l= 1.94Å,h=1.70Å and θ=60° for the Cu adsorption. The corresponding bonding energies for two systems are 62.1 and 21.3 kcal/mol, respectively. These results are consistent with the experimental fact. The origins of the different bonding energies are discussed and the origins of the different values for the activition energies are explained by molecular orbital natural correlation.