A new type of epoxy resin, which contained phosphorus oxide and nitrogen groups in the main chain, was synthesized. The structure of the new type of epoxy resin was confirmed by infrared (IR) spectroscopy, H-1 nuclear magnetic resonance (H-1-NMR;IR), and C-13-NMR spectroscopic techniques. In addition, compositions of the new synthesized epoxy resin (TGDMO) with three curing agents, for example, bis(3-aminophenyl) methylphosphine oxide (BAMP), 4,4＇-diaminodiphenylmethane (DDM), and 4,4＇-diaminodiphenylsulfone (DDS), were used for making a comparison of its curing reactivity, heat, and flame retardancy with that of Epon 828 and DEN 438. The reactivities were measured by differential scanning calorimetry (DSC). Through the evaluation of thermal gravimetric analysis (TGA), those polymers which were obtained through the curing reactions between the new epoxy resin and three curing agents (BAMP, DDM, and DDS) also demonstrated excellent thermal properties as well as a high char yield.