Minimal quantity lubrication (MQL) is a green manufacturing technology for cutting. In order to understand the influence of MQL system on turning residual stresses，the influence of air pressure, amount of lubricating fluid, spray distance and oil mist temperature of MQL system on machining residual stress were studied by orthogonal test of 45 steel turning.The results show that the influence of oil mist temperature on the residual stress is the greatest, the amount of lubricating fluid also has a certain effect, and the influence of airpressure and spray distance is not significant. The residual (tensile) stress decreases with the decrease of temperature of oil mist. The residual (tensile) stress decreases with the increases of amount of lubricant of the. The influence mechanism of MQL system on machining residual stress is to change the thermal effect of thermal coupling of residual stress by changing the cooling capacity and permeability of oil mist.