The accurate control of oil-water-air volume and its atomization effect by the minimum quantity lubrication (MQL) device directly affect the cooling and cutting performance, thereby influencing the machining quality of parts. To improve the auxiliary cutting effect of the MQL device, a digital MQL device with oil-water-air mixing has been designed and developed to improve the continuity and uniformity of lubricant mist spray. Based on MQL atomization technology, an experimental platform for the milling process has been constructed to test its auxiliary cutting effect. The results show that the developed oil-water-air mixing digital MQL device significantly improves the quality of oil mist and the auxiliary cutting effect.