Two kinds of unidirectional PAN M40 carbon fiber (55%, volume fraction) reinforced 6061Al and 5A06Al composites were fabricated by the squeeze-casting technology and their interface structure and thermal expansion properties were investigated. Results showed that the combination between aluminum alloy and fibers was well in two composites and interface reaction in M40/5A06Al composite was weaker than that in M40/6061Al composite. Coefficients of thermal expansion (CTE) of M40/Al composites varied approximately from (1.45-2.68)×10-6 K-1 to (0.35-1.44)×10-6 K-1 between 20 ℃ and 450 ℃, and decreased slowly with the increase of temperature. In addition, the CTE of M40/6061Al composite was lower than that of M40/5A06Al composite. It was observed that fibers were protruded significantly from the matrix after thermal expansion, which demonstrated the existence of interface sliding between fiber and matrix during the thermal expansion. It was believed that weak interfacial reaction resulted in a higher CTE. It was found that the experimental CTEs were closer to the predicted values by Schapery model.