Cyanate ester resins modified by monofunctional cyanate ester had been synthesized. Characterization of the resins had been carried out including polymer reaction activity, rheology and dielectric performance. Results indicated that monofunctional cyanate ester partly inserted the polymer network during the final curing stage and improved the reaction degree of cyanate groups. The cured cyanate ester exhibited a lower dielectric constant ranged from 2. 8 to 2. 9(7 ~18 GHz) and a lower dissipation factor than those of the cured BADCy resin.