According to ASTM standard test methods and conditions,the oxidation and total acid number(TAN)of lubricants under actual conditions were measured by Fourier transform infrared spectroscopy and automatic potentiometric titration separately,and the correlation model between oxidation and TAN was studied.The results show that the degree of oxidation and the total acid number are highly relevant in the whole,the oxidation determined by infrared spectroscopy can be used to replace TAN measured by potentiometric titration.However,the relationship between total acid number and oxidation is different for different types of oils.The theoretical calculation of total acid number by oxidation need to have a sufficient number of measured data base of samples.