Abstract: Based on interference principle of light, the length of Fabry-Perot cavity and an optical fiber F-P interferometer was obtained. The contactless type laser ultrasound experimental system of optical fiber was established and used for detecting the crack of aircraft engine blade. The optical fiber F-P sensor realized many bundle lights interference measurement using single optical fiber, which was easy to fabricate and with low cost, as well. It could detect the crack of blade efficiently, fast and contactlessly.