The failure process of unidirectional BN-coated HI-NICALON(TM) SiC fiber reinforced glass matrix composites was examined under tensile loading. In situ observation of the mean matrix crack interval was conducted by the replica observation during tensile testing. Axisymmetric cylindrical models extended to the system considering the strength distribution of fibers were proposed to predict the whole stress-strain curve for comparison with the experimental results.