Abstract: The graphite flakes reinforced Al matrix composites (50vol%G_f/6061Al) were fabricated by powder metallurgy technique. The G_f had a well bonding with Al matrix without cracks and pores. The composites were exposed to a thermal cycling test in the temperature range of −50-120℃. The microstructure and properties of 50vol%G_f/6061Al were examined when the composites were tested by 10, 50, 100 and 200 thermal cycles. The density of the composites is almost unchanged under different thermal cycles. With the number of the thermal cycle increasing, the G_f in the composites are cracked due to the stress from the difference of the thermal expansion coefficient between G_f and Al matrix. The strength and thermal conductivity of the composite are decreased with the number of the thermal cycle increasing. After 100 thermal cycles, the bending strength decreases by 27.4% and thermal conductivity decreases by 11.5% compared to that of the sample without thermal cycles. The broken G_f and the cracked interface between G_f and Al matrix could release the thermal stress, therefore, the cracking of the G_f would be retarded. The microstructure and properties of the composites are not serious changed. After 200 thermal cycles, the bending strength decreases by 32% and TC decreases by 13.1% compared to that of the sample without thermal cycles.