Based on the theory of correlated-basis-functions, and with the "big molecular" model, we have presented a new theory of hydrogen chemisorption on metal surfaces. Through the variational numerical calculation with respect to the parameter of position of adatom, we obtained chemisoption energies, electron densities, and equilibrium distances for the hydropen chemisorption on metals Al (rs = 2.07), Mg (rs = 2.66), Li (rs =3.28) and Na (rs =3.99) We also made a comparison with some other representative theories.