To research the microstructure change in nanomachining process,a coupling nanofretting nanomachining model of single crystal copper is presented using molecular dynamics methods,and nanocutting processes are simulated.By angle distribution function(ADF) and radial distribution function(RDF),the structure changes of subsurface in material are analyzed,and the results show that there exists an unstable phase transition from the close-packed hexagonal structure to face-centered cubic structure in the subsurface of single crystal copper during coupling nanofretting nanomachining process.