A method of quantitative detection of the concentration of dissolved water in lubricant by grating infrared(IR)spectrum was studied.The principle of grating IR spectrum method applied to the quantitative detection of dissolved water in lubricant was presented,and methods and interference factors for detecting the dissolved water in lubricant were discussed.The results show that the grating IR with the resolution of 15 cm-1 can meet the requirements of quantitative detection of dissolved water in lubricant.Through integration of multi element linear regression and SIMCA lubricants classification,quantitative detection on site of dissolved water in lubricant can be implemented and interferences of other pollutants can be reduced.The method of IR spectrum can greatly simplify the oil analysis process on site with less influence from environment,which can be widely applied for oil testing projects in offline laboratory and onsite.