Abstract: By using Mori-Tanaka equivalent method, the C/SiC bundle with voids was treated as a double inclusion problem and the effective elastic moduli of the bundle were calculated. A new predictive model of elastic properties for 2.5D-C/SiC composites is developed with the consideration of the incomplete linkage of the C/SiC bundles. The relationship between the volume fraction and shape of voids in C/SiC bundle and elastic properties were obtained by the predictive model. The calculations disclose that the shape of voids has little effect on elastic properties of composites, and the void volume fraction has obvious effect on elastic properties of 2.5D-C/SiC composites. The degradation coefficients were given by the real contacting area ratio of warps and the elastic parameters of the 2.5D-C/SiC composite were calculated, and the comparison with theoretical and experimental results demonstrates that the new model is more accurate.