Abstract: A study about fiber breakage and its affected region was presented.Some results of numerical analysis and experiment were obtained by evaluating a feasible simple model based on crack propagation statistic theory.The cxperiment studied the boron fiber breakage and its affected region in titanium matrix composites.The results indicate stress redistribution and concentration due to broken fibers obviously affect the stress-strain condition of the other neighboring unbroken fibers.Accompanying with cumulative process of fiber breakage,the original crack extend and its affected region (also affected length)successively enlarge.In metal matrix lower volume fraction fiber-reinforced composites,the work hardening of matrices also affect the process of fiber and composites damage.