Abstract: The influence of interface debonding on matrix cracking of cross-ply SiC/calcium alumino silicate glass (CAS) composites under uniaxial tensile loading was studied by micromechanics approach. The fracture mechanics interface debonding criterion was used to determine the interface debonding length in the 0? ply. When cross-ply ceramic matrix composites are under tensile loading, transverse cracking in the 90? ply and matrix cracking in the 0? ply occur. Based on the difference of the transverse crack and matrix crack, the damage states in cross-ply laminates can be classified into five modes. The mode 3 cracking mode contains transverse cracking, matrix cracking and fiber/matrix interface debonding. The mode 5 cracking mode only contains matrix cracking and fiber/matrix interface debonding. The critical stress of mode 3 and 5 was determined using the energy balance method. The effects of interface shear stress and interface debonding energy on matrix cracking stress have been analyzed. The conclusions that the initial cracking stress of mode 3 and 5 increases as the interface shear stress and interface debonding energy increases was gotten. The analysis was compared with the experimental result of unidirectional fiber-reinforced ceramic matrix composites done by Chiang. The predicted trend of cross-ply ceramic matrix composites is consistent with the experimental results of unidirectional ceramic matrix composites.