To analyze the thermal expansion behavior of SiC particle reinforced Al-Si alloy matrix composites, a new model for the CTE of bi-dispersed composites was introduced, following the model for monodispersed binary composites which we suggested earlier. In this new model, it was also considered that during cooling relaxation of residual stresses can create elastoplastic deformation zone around both SiC and Si particle in the matrix. The interacting effect among the reinforced SiC particle, crystallized Si phase and soft matrix is considered by introducing the influence of the elastoplastic deformation zone around each particle. This new CTE model for bi-dispersed composites was found to be able to apply to the multi-phases composites.