A novel aryl phosphinate epoxy ether, 10-(2＇,5＇-bis(glycidyloxy)phenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DHQEP), was synthesized. The structures of the obtained compounds were confirmed by mass, FTIR,H-1, C-13, P-31-NMR spectroscopies, elemental analysis, and X-ray single crystal analysis. In addition, compositions of DHQEP with common curing agents, e.g., 4,4＇-diaminodiphenylmethane (DDM), 4,4＇-diaminodiphenyl sulfone (DDS), and dicyanodiamide (DICY), were studied to compare their thermal and flame resistance with that of commercial epoxy resins. The aryl phosphinate epoxy-resin composites exhibited excellent thermal properties and a quite high limiting oxygen index (LOI) value as well as high char yield. Aryl phosphinate epoxy ether is shown to be an effective flame retardant and thermal stabilizer for epoxy resins.