The density functional theory (DFT) of first-principles studies were adopted to calculate adsorption of H2 on Mo(001) surface. The structure parameters and the adsorption energy at three adsorption sites (top, bridge, hollow) of H2 on Mo(001) surface were obtained. The calculation results show that the highest adsorption energy is at the top site. The changes of the nearest distance between H atom and Mo atom dH-Mo with the H2 molecule bond length before and after the adsorption were analyzed. From the analysis of the density of states of H2 and the adsorption of H2 on Mo(001) surface, the adsorption reasons is the interaction between the 1s orbit of the H2 molecule and the 4d orbit of the base metal