Abstract: Benzoxazine (BO) resin modified cyanate ester (CE) resins were prepared by solvent blending method. Their curing behaviors were studied by Differential Scanning Calorimetry (DSC). Their curing shrinkages were investigated by density measurement. The thermal properties, hygrothermal resistance and mechanical properties of the modified resins were also investigated. The results showed that the modified resins offered good processability which could be cured without any catalyst. Their onset temperatures of curing reaction decreased by more than 25℃ with outstanding autocatalysis. The resins were cured with no shrinking but slight swelling to form low density cured resins. The heat resistant performance of the cured resins slightly decreased compared to the cyanate ester resin. The glass-transition temperature (T_g) and onset decomposed temperature of 5% benzoxazine modified cyanate ester resins decreased by 20℃, and the char yield increased by 0.2% at 1 000℃ compared to the cyanate ester resin. The water uptake rate of the cured resins was lower than 3% after 72 h in boiling water. Flexural strength of the cured resin reached 144.6 MPa, and flexural modulus was 4.44 GPa. The retention rate of flexural strength was 63% after wet and heat aging and the flexural modulus rose to 4.62 GPa, which showed good humidity and heat resistance.