Abstract: PM915 resin was prepared by modifying cyanate ester resin with polyethersulfone (PES). The processability and cured resin properties of PM915 resin were investigated systematically. The PM915 resin has excellent process performance, good film-forming property and better storage stability, and could be used to prepare prepreg by hot melting method. The process properties such as rheological property and gel time of PM915 resin were measured. The results show that the viscosity of PM915 resin at 70℃ is about 20 Pa·s, the viscosity of the resin can keep stable for 115 min at 120℃, and the gelation time is 40 min at 160℃. Due to the release of some reaction heat in the preparation process, the curing exothermic enthalpy of PM915 resin decreases, and the curing temperature of PM915 resin is 220℃. The curing shrinkage of PM915 resin is as low as 0.16% due to the introduction of PES. The temperature at 5% thermal weight loss T_d5, glass transition temperature T_g and thermal expansion coefficient of cured PM915 resin are 423℃, 276℃ and 4.4×10⁻⁵/℃, respectively, which indicates that the cured PM915 resin possesses excellent thermal properties. After modification, the toughness of the cured resin has been greatly improved owing to the introduction of flexible groups. The flexural strength and modulus of the cured PM915 resin are 139.3 MPa and 4.2 GPa, the tensile strength and modulus of the cured PM915 resin are 75.8 MPa and 3.8 GPa respectively. What’s more, the investigation of fracture surface by scanning electron microscope (SEM) indicates that the cured PM915 resin exhibits toughness fracture. Therefore, the PM915 resin is a kind of ideal resin matrix for fiber reinforced prepregs by hot melting process, and possesses low curing shrinkage, high dimensional stability and heat resistance, which can be used in satellites and other spacecraft.