Based on the DMT contact model,the friction force and friction coefficient of nano-friction on diamond surfaces were calculated.An atomic force microscope was used to study the tribological characteristics of the diamond specimens by mechanical polishing and focused ion beam (FIB) etching in the atmospheric environment,with diamond probes and flaky diamond specimens as friction pairs.The experimental results were compared with the calculated results of the DMT contact model.The results show that the friction coefficient decreases with the increase of the load,which is consistent with the previous research on diamond micro-friction.The calculated results of the DMT contact model are in good agreement with the experimental results of mechanically polished surfaces,but slightly higher than the experimental results of FIB etched surfaces,verifying the applicability of the DMT model in the study of diamond nanofriction.Through the surface roughness and carbon atom chemical state analysis,it is found that the hindering effect of rough surfaces on probe sliding and the friction reduction effect of amorphous carbon produced during FIB etching are the reasons for the differences in the DMT model applied to the above two machined surfaces.