Minimal quantity lubrication (MQL) is a green manufacturing technology. Based on thermal coupling theory on machined residual stress formation，there was a turning experiment to understand how MQL affected turning residual stresses，and the experiment materials were 45 steel, 40Cr steels(hardening),40Cr steels（annealing）and 304 stainless steel. In the experiment，the residual stresses, the cutting force and the cutting temperature were obtained in dry cutting, air cooling cutting, wet cutting and MQL. Then, the reasons were analyzed for the different distribution of the residual stress in all lubrication methods，and laws and mechanism were obtained about how MQL affected residual stress. The experiment results have shown that MQL helps to reduce residual tensile stress, MQL has obvious impact on high toughness and strength material, its impact on materials difficult to cut is greater than ordinary carbon steel, and the inhibition of thermal effects by MQL is the main mechanism which affects residual stress.