We have established the non-relativistic and relativistic atomic configuration interaction methods to calculate excitation energies of low excited states as well as radiative transition probabilities for allowed and forbidden transitions. In order to check our computer codes, we have calculated the excitation energies for N=2 states and the corresponding radiative transition rates for the atomic helium. The results of our non-relativistic and relativistic calculations agree with each other. The excitation energies are accurate within a few thousandths, the corresponding radiative transition probabilities within a few percents. Our methods can be readily applied to other atoms as well as ionized atoms.