In this research the effect of electron correlation can be described by evaluating the difference in the one-particle radial distribution function. The other effect of the electron correlation can be described by evaluating Coulomb hole. It also can be described by evaluating the change which occurs in the two-particle radial distribution function to study the radial correlation for He atom and compared the result with the series of He-like. Four types of wave functions can be used in this research, the Hartree-Fock HF (uncorrelated wave function), configuration interaction, Eckaret-Hyllears and Simple Configuration-Interaction wave functions. We conclude that the difference in one-particle increase as Z increase and the location is closed to nucleus. And the radius of Coulomb hole decrease and the area increase as Z increase. Also the radius of Coulomb hole for Configuration-Interaction and Hartree-Fock wave function is larger Simple Configuration-Interaction and Hartree-Fock wave function is larger Eckart-Hyllears and Hartree-Fock wave function for He atom. And the change in the two-particle increase and the location of this change decrease as Z increase. Also we conclude that the electron correlation increase as Z increases. The properties and parameters studied in this work:-1.The inter-particle distribution function f(r12). 2.Two-particle distribution function D(r1, r2). 3.One-particle distribution function D(r1). 4.The inter-particle expectation value _r12_ . where -2?n?2. 5.One-particle expectation value _r1_ where -2?n?2.6.Coulomb Hole ? f (r12). 7.Partial Coulomb Hole.8.The change ?DCI-HF (r1, r2) which occurs in the two -particle radial distribution function. All results were obtained numerically using computer program (MathCAD/ 2003).