  We study the influence of anisotropy of the impurity potential on isotope
coefficient of an impure superconductor in Born limit. From the isotope
coefficient of non-magnetic and magnetic impurities including an angle-resolved
Fermi surface density of state, anisotropy order parameter and impure
potential, we make the assumption that the form of them are in the harmonic
form and are investigated. Our numerical calculation of isotope coefficient can
fit well with experimental data of high-Tc superconductors.
