Abstract: At the early stage of rail transit vehicle debugging and operation，the low air compressor operation rate will easily cause the lubricating oil emulsification of screw air compressor unit. By using the emulsifying control method，the air compressor will run 30 min continuously every time when the vehicle is powered on to improve the lubricating oil temperature of lubricating oil moisture evaporation，avoid the phenomenon of lubricating oil emulsification，aiming to improve the service life of the lubricating oil effectively.