Abstract: The method of micromechanics was used to study the matrix failure mechanism of UD-C/SiC ceramic matrix composites (CMCs). Shear-lag theory model and critical matrix strain energy (CMSE) were employed to forecast the tensile process, and the stress-strain curves of UD-C/SiC CMCs matrix cracking and failure were obtained. Extended finite element method (XFEM) was also utilized to simulate this process and the relative stress-strain curves were obtained. It is indicated that the calculation results of the two different methods are in accordance with that of the experiment. And it is proved that both of the two methods are valuable to forecast the matrix failure property of the UD-C/SiC CMCs.