Abstract: Adhesive contact is one of the major reasons that cause the failure of MEMS. It is an efficient approximation method to carry out contact simulation in nano -scale based on Hamaker hypothesis. The continuous method works can only be used to calculate long range attraction, because it neglects the microstructure of the surface of the object. A new numeral method considering adhesion of structure of surface atoms is put forward through improvement, which is more accurate in short range and can be used to calculate repulsion. The method is of certain guiding significance for designing MEMS.