Abstract: The thermal cycling test is carried out for the M40/cyanate ester composites. The mass loss ratio, the bending strength and the interlayer shear strength of the specimens are measured after different thermal-cold cycles. The fracture surfaces of the specimens are observed by SEM. The results show that the material sample has a small mass loss ratio with the increase of the thermal-cold cycles. In addition, the bending strength and the interlayer shear strength of the composite increase firstly and then decrease slightly after 150 cycles. The SEM analysis shows that the integrating state of the interface between the carbon fiber and the resin matrix is good.