Abstract：The friction behaviors between rigid spherical tips with different atomic scale rough topography and the elastic flat substrate are simulated using large-scale molecular dynamics method .The relationship between friction and load, real contact area and load, friction and real contact area are analyzed for non-adhesion and adhesion to study the friction behavior laws on nanometer scale. The results show that the relations between real contact area and load of the studied systems are all agree with the corresponding continuum contact models, such as Hertz smooth contact model, Greenwood-Williamson rough contact model and Maugis-Dugdale adhesive contact model. For the non-adhesive contacts, the friction-load relations are linear for both smooth surface system and rough surface system, while there is no simple relationship between friction and real contact area. However, the relationships between friction and real contact area are linear for the adhesive contacts, while the friction-load relations are sublinear and agree with Maugis-Dugdale model prediction. Our research shows that when changed from non-adhesion to adhesion, the decisive factor of friction will transfer from load to contact area, and the friction behavior will transfer from load-controlled friction to adhesion-controlled friction.