Hydrogenation reactor, a typical equipment in petrochemical industry, usually works in tough condition, such as high temperature, high pressure, with hydrogen gas as medium. 2.25Cr-1Mo is widely used as reactor material. However, with the increase of operating condition, a better material is needed. At present, 2.25Cr-1Mo-0.25V is proved having a better mechanical property in high temperature than that of 2.25Cr-1Mo. Hence, it is very important to study the hydrogen impact on 2.25Cr1Mo0.25V. This paper aims to study the relationship between H atom and metal crystal from microscopic view. Based on the first-principles calculation, the convergence analysis of parameters, the adsorption of H atom on Fe, V and their surfaces have been discussed. The results show that the parameter values of simple crystal surface (110) are less than surface (100), such as energy cutoff, k-point sampling, especially the number of slab layers. Tetrahedral-site is the stable site when H atom exists in bbc Fe, V lattice. And quasi three-ford site is the stable status when atomic H absorption on Fe(110) and V(110).