To better understand the influence mechanism of transition metal elements (Ti, V, Ni, Mo) on the nucleation of chemical vapor deposition (CVD) diamond coating, the intrinsic mechanism of the CH3 adsorption on impregnated diamond cemented carbides through geometry, interaction energy, Mulliken charge distribution, visualization of the interactions, charge density difference and density of state (DOS) were investigated theoretically. All the calculations were performed by density functional theory. The calculated results indicate that diamond surface doped with Ti/V/Ni/Mo, rather than pure diamond surface, exhibits stronger interactions. The adsorption capacity is related to the valence electron structure of each atom, and the surface doped with Ti has the most stable adsorption capacity. The charge transfer between CH3 and Ni is more easier to form covalent bond, Mo is beneficial to promote the dehydrogenation reaction of CH3. Ti, V, Ni and Mo are conducive to increasing the nucleation density and improving the strength of CVD diamond coating.