The mechanism of the scattering of high energy proton with nuclear is similar with that of Fraunhofer diffraction of circular hole .The extreme value of differential cross section of the former one corresponds to that of light intensity of the latter one .With this relation ,we can determine the nuclear radius and extract the nuclear radius constant .We shown the relation and constructed the calculation method .Employing the method ,we calculate the constant nuclear radius at extreme value of differential cross section .The res...