Abstract: Monitoring damage and repairing crack are the important problems in composite materials. The method of self-diagnose and self-repair composite structures using a hollow-center optical fiber filled adhesive is a good technique. Based on this thought, the mechanism investigation and analysis of light transmission in the hollow-center optical fiber are made in detail. The measure method and experimental research of self-diagnose for the rupture location in composite materials are also put forward. In this paper, the performance of the hollow-center optical fiber is explained first. The theory of light transmission attenuation by snipping the optical fiber is used in self-diagnose of the rupture location. Finally, a Y coupler is given to measure the rupture location and a general experimental system for self-diagnose and self-repair is given as an example.