Structures of environmental friendly phosphorous flame-retardant polyester were characterized through infrared spectra (IR), the performance of its properties such as intrinsic viscosity, differential scanning calorimeter (DSC), oxygen index (OI) and its spinnability was investigated. The results show that the flexible segments in phosphorous flame-retardant monomer were also introduced into the backbone of the polyester macromolecules, which causes the decrease of the phosphorous flame-retardant polyester glass transition temperature (θ _g) and melting transition temperature(θ _m). The synthesized phosphorous flame-retardant polyester resins have a very good flame retardantability and spinnability; when the mass fraction of phosphorous flame-retardant monomer was 4.5%, the oxygen index of phosphorous flame-retardant polyester reached to 32.8%. The tensile strength and crystallinity decreased owing to the much more space volume of phosphorous flame-retardant polyester. The results indicate that the properties for phosphorous flame-retardant polyester can satisfy the requirements for the manufacture of polyester fibers.