The TiC-coated diamond/Al composites with 65% diamond in volume fraction were fabricated by gas pressure infiltration method.The microstructure and coefficient of thermal expansion（CTE） were analyzed and measured,respectively,to understand the thermal expansion behavior of the TiC-coated diamond/Al composites.The results show that the uniform distribution of diamond particles in the Al alloy with compact microstructure can be observed.The TiC coating is considered to improve selective interfacial bonding between diamond particles and Al alloy effectively and enhance the interfacial bonding.The CTE of the composites is decreased obviously as a result of TiC coating.The CTE of composites with TiC coating can be predicted by the mean value of the Turner and Kerner models,while the CTE of the composites without coating can be predicted by the Kerner model.