A novel amino terminated poly(phthalazinone ether ketone） (A-PPEK） was synthesized from 4-(4-hydroxylphenyl）(2H）-phthalazin-1-one, 4,4'-difluoro benzophenone and 4-aminophenol by a two-step one pot method, and its curing properties for phthalonitrile resin were investigated. Compared with the commonly used aromatic diamine curing agent 4,4 '-diaminodiphenyl sulfone (DDS）, the 5% weight loss temperature of A-PPEK was increased by 69.3 ℃. Moreover, unlike the rapid sublimation of DDS at 400 ℃, A-PPEK can still retain more than 95% of the mass at the same temperature, indicating that A-PPEK can effectively solve the problem of defects in phthalonitrile resin caused by the decomposition of small molecule curing agent at high temperature. A series of tests showed that the system of resorcinol phthalonitrile resin DPPH cured with A-PPEK had excellent heat resistance and processability: the maximum 5% weight loss temperature of the cured resin can reach 553.2 ℃, the glass transition temperature was higher than the experimental test temperature of 380 ℃, and the minimum viscosity can reach 0.2 Pa?s.