Abstract: Cyanate ester (CE) resin, which has high glass transition temperature, low curing shrinkage and excellent dielectric properties, is commonly used as the material of high temperature resistant or microwave absorption in the aerospace field. However, after high temperature curing, the poor immigration adhesion between CE resin and carbon fiber (CF) would result in brittleness of its composite product. In addition, the preparation process of composites is complex, resulting in delamination damage. Therefore, the product quality and practical application are considerably affected. In this paper, polyether sulfone (PES) was used to modify CE resin and prepare prepreg. It prepares prepreg with good wettability and can apply to various dry forming composite preparation processes. The results show that the introduction of PES can significantly enhance the mechanical properties and thermal stability of CF/CE resin matrix composites. Compared with the CF/CE unidirectional plate, the flexural strength of 7.5wt%PES-CF/CE unidirectional plate is increased by 17%; the interlaminar shear strength is increased by 31%; the impact strength is increased by 39%; and the longitudinal thermal expansion coefficient is reduced from −2.07×10⁻⁸ K⁻¹ to −10.7×10⁻⁸ K⁻¹; the transverse thermal expansion coefficient is reduced by 20%. The modification effect is signifi-cant.