In this paper we described an optic fiber Mach-Zehnder interferometer constructed with metal coating fiber. The metal coating fiber is designed specially for monitoring the deformation in composite material. It has high sensitivity for stress and vibration applied on it and has low sensitivity for temperature. And it can be used to measure the force applied on it in a high temperature environment, more than 300 degree(s)C. The sensitivity for deformation measurement is better than 1 micrometers . The design of the metal coating fiber and its characteristics are given in this paper. And the measurement results of a fiber Mach-Zehnder interferometer for composite material are given too.