Abstract: The energy levels for the ground states of helium-like atom systems are calculated by virtue of vari- ational method and the twoparameter trial wave function which includes the correlation coordinate between the two electrons of helium-like atoms. The numerical resuhs are in good agreement with the experimental data. The calculated results indicate that the accuracy of the theoretical results can be effectively improved by introducing explicitly the correlation coordinate in the trial wave function and the correlation effects between electrons may influence the ground state energy of helium appreciably.

Key words: helium-like atom, ground state energy, variational method, electron correlation