Abstract: Two kinds of unidirectional laminates made of carbon/cyanate composite named M40/DFA-1 & M40/DFA-N3(nano TiO ₂ contained) are selected for studying the effects of atomic oxygen interactions. Based on the ground simulation of atomic oxygen environment, several tests are conducted, such as the surface/fracture morphology observation, the mass loss test, the inter-laminar shear strength test, and the X-ray photoelectron analysis of surface components. After the exposure of 1.5×10²⁰ cm^-2 atomic oxygen, the surface detachment is observed on both types of materials. In addition, the mass loss as well as the erosion rate are calculated. It is shown that the M40/DFA-N3 sample exhibits relatively higher mass loss and erosion rate while with a smaller decrease of the inter-laminar shear strength compared with the specimens made of M40/DFA-1. It can be partly attributed to the drastic oxidation reaction within the nano TiO₂ granules, which leads to a higher proportion of C=O bonds generated.