:DOPOMA was synthesized by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) and maleic anhydride(MAH), then it with dicarboxylic acids and diols by polycondensation reaction to get the side chain phosphorus hydroxyl-terminated saturated polyester, then it with TDI, DMBA and DEG as chain extenders,TEA as neutralizer to synthesis phosphorus flame retardant waterborne polyurethane. Chemical composition, thermal stability, charring performance, morphology and mechanical properties of phosphorus-containing polymer were investigated by Infrared analysis(FT-IR), Thermogravimetric analysis(TGA), Limiting oxygen index (LOI), Scanning electron microscope (SEM), universal tensiletest machine.