According to four potential energy surfaces of MP4 and SCF with/without counterpoise (CP) procedure, the influence of electronic correlation effect and CP to remove the superposition errors on the equilibrium geometry of He-H2O complex is discussed and accurate equilibrium geometry of He-H2O is obtained. It is shown that the applications of both electronic correlation and CP are necessary in the calculations of weak van der Waals complex, by means of effective basis set.

Key words: WATER, COMPLEX COMPOUNDS, HELIUM, POTENTIAL ENERGY SURFACES