New phosphorylated epoxy-imide polymer was obtained using diimide-diepoxide (DIDE) cured with bis(3-aminophenyl)methylphosphine oxide (BAMP). In addition, composition of the synthesized diimide-diepoxide (DIDE) with common curing agents, e.g., 4,4’-diaminodiphenylether (DDE) and 4,4’-diaminodiphenylsulfone (DDS), were used for making a comparison of its curing reactivity, heat and flame retardation with that of bis(3-aminophenyl)methylphosphine oxide. The reactivity of those curing agents toward epoxy-imide, as measured by differential scanning calorimetry (DSC), was of the order DDE > BAMP > DDS. Through the evaluation of thermal gravimetric analysis (TGA), the new phosphorylated epoxy-imide polymer demonstrated excellent thermal properties as well as a high char yield.