The antifriction effect of molybdenum dialkyl dithiocarbamate(MoDTC)is directly related to its content in lubricating oil.In order to explore a rapid and accurate detection method of MoDTC content in new and used lubricating oil,the infrared spectroscopy characteristics of MoDTC in gasoline engine oil and gearbox oil were analyzed.The absorption peak with wave number of 1 515 cm-1 was selected as the quantitative standard,and the determination methods of MoDTC content in engine oil and gearbox oil were established by spectral subtraction method and direct trend method respectively.This method has high correlation coefficient of regression curve and very little calculation error.The consumption of MoDTC in gasoline engine oil during the four ball test was investigated by the established method.It is found that the consumption trend of MoDTC has a good corresponding relationship with the changing of friction coefficient and wear scar diameter in the four ball test.It is verified that this method has a good effect on the determination of the content of MoDTC in both new oil and used oil.