Traditional methods to measure the the rmal expansion coefficient of materials are greatly influenced by the external environment factors and the test methods and instruments are also complex.This paper proposes a new method that uses a micro fiber Fabry-Perot (F-P) sensor to measure the expansion coefficients of the optical fiber itself and aluminum at room temperatur e.This paper describes the technology in detail where the FP sensor is produced by using hydrofluoric to ac id th e optical fiber.In a temperature range of 30℃ to 120℃,the thermal expansion coefficient of the fiber is meas ure d to be 5.2E-8K-1.At the same time we paste the FP sensors on a metal aluminum,and measure the thermal expansion c oe fficient of the metal aluminum to be 23.25E-8K-1.Experimental results fit well with the theoretical values .Also the causes of error were analyzed.Experimental result shows that this testing method by using the micro fiber FP sensors is stable and reliable,also the production process is easy.The fiber-optic F-P sensor developed in this work is easy to fabricate and has a b road sensing application field.