Abstract: A Preliminary model for the analysis of thermo-mechanical behavior of interfacial coating on fibers in unidirectional composites was developed on the solution of thermo-elastic mechanics.The low modulus coating can effectively reduce the interfacial stress caused by different thermal expansion coefficient between fibers and matrix,no matter how high or low the expansion coefficients of coatings are in CF/Al and SiC/Ti systems,however,high modulus coating can decrease the interfacial compressive stress,only when the thermal expomsion of coating is low.