In this paper，a method for measuring linear expansion coefficient of metal based on the Fabry-Perot

( F-P) etalon is proposed. The elongation of metal rod during thermal expansion can be converted into the

change of interference fringe radius in interference optical field of F-P etalon via optical lever. The linear expansion

coefficient of metals can be obtained by measuring the distance between interference fringes. It only needs to measure

the distance between the outer fringes of the interference optical field by the F-P etalon，and the multi-beam equal

inclination interference of the F-P etalon can produce sharp interference fringes，the measurement process is

much simpler，and the accuracy of the measurement result is much higher. The experiment results have demonstrated

the feasibility and reliability of the method.