Abstract: Trajectory simulations are carried out for vibrationally assisted adsorption of H2 on Cu(100) surface. The potential-energy surfaces for H2 approaching the copper surface in any molecular orientation are obtained by using the embedded-atom method. It is clearly shown that the vibrational energy of incident H2 greatly promotes the dissociation by assisting H2 to surmount the activation barrier at the reaction zone. The dependence of initial sticking coefficient S0 for H2 activated adsorption on Cu(100) surface on the normal incident translational energy EN has been calculated. The different contributions from H2 (v = 0) and H2 (v = 1) to the sticking probability of H2 molecular beam adsorption on Cu(100) are investigated. The results are in well agreement with the experimental observations and other theoretical calculations.