Abstract: For the past three decades,many optical metheds for the measurement of lubricationfilm thickness have been widely studied,and some metheds have been developed. However,themethods usually are not of enough resolution and precision if they are used for measarement ofnanometer lubrication film. According to the basic principles of the optical interference, the presentpaper proposed a method for nanometer lubrication film thickness measurement by using relativelight intensity principle,and had developed a NGY-2 inter ferometer with a special design in lightroute. The measured results under the given working conditions show that the meter is of advantageswith high resolution afid precision, and with high resistance to the variation of the outside light fieldas well.