Microwave digestion was used as the efficient method for lubricating oil samples pretreatment.Three trace nonmetal elements of S,P and Si in lubricating oil were detected by Inductively Coupled Plasma Optical Emission Spectrometer(ICPOES).The optimum analysis parameters of the instrument were established,such as wavelength,emission power,flux of sprayer and height of viewing,and the determination method of trace nonmetal elements in lubricating oil by ICPOES and microwave digestion was established.The spiked recoveries of the method are in the range of 93% to 1012%,and the relative standard deviations(n=7) are no more than 3%.It is a efficient,accurate and sensitive method for the determination of trace nonmetal elements in the lubricating oils.