Abstract: First of all,the development of inherent damage near notch tip in 3D carbon carbon was examined with polariscopic microsocpe while loading.The notch tip was tracked with a specially designed adjustable stand and loading appratus during testing.Bascd on the obserction,a very simple analytical model was cstablished.In order to use micromcchanics to prediet the notched strength,the strength of in-situ fiber bundle was measured with a specially dcsigncd fixture.The strength of 3D carbon carbon is dominated by the longitudinal strength of the portion of fiber bundle,where the stress concentration takes place.Hedgepeth's stress concentration factor for infinite plate is corrected for finite plate.Calculation of stress concentration factors of fiber bundles near notch tip also shows that failure of a single fiber bundle will cause total rupture of the spacimen.With Zweben's statistical strength criterion,the strength of the notched 3D carbon carbon was predicted and the prediction agrees with experimental results quite well.