Close-coupling equation is applied to the 3He(4He)-H2 system，and the rotational excitation cross sections for incidence energy of 05eV are calculated.By analyzing the differences between these partial wave cross sections and differential cross sections，the change of the partial wave cross sections and differential cross sections with increase of quantum number，as well as with the change of the mass of isotope atom are found out. Based on the calculation，the effect of isotopic substitution on atom-diatom collision is discussed.