Abstract: An optical low-coherence system including Mach-Zehnder interferometer is designed and applied to measure material micro cracks. Light signals are received by a balance detector, and are collected and then stored on LabVIEW platform. Images of micro cracks are reconstructed based on two-dimensional information of engine blade cracks. Its resolution is up to 15.6 μm. This method has advantages of noninvasion and high resolution.