Hamaker summation method is used to approach the tip-surface interactions for rutile TiO2 surface with Si-tip in non-contact AFM. The calculated results show that the Hamaker summation method gives tip-surface force the periodical nature with the peak at O2- positions at the tip-surface distance of about 1.5 Angstrom, and abruptly at Ti4+ and O2- ion positions at the tip-surface distance of about 1 Angstrom on rutile TiO2(001) surface along [110] direction. (C) 2004 Elsevier B.V. All rights reserved.