Abstract: The slip stress acting on straight screw and edge dislocations in surface layer of pure aluminum was investigated based on the analysis of dislocation image force. The size of low dislocations' density area of the surface layer and the critical slip distance of the dislocations induced by image stress effects were calculated theoretically. The relationship between critical climb distance and temperature of straight edge dislocation was discussed. The relatively stable dislocation configuration around the surface layer was indicated.