The high viscosity phosphorus-primarily based flame retardant polyester chip become dried, and the low viscos-ity phosphorus-based totally flame retardant polyester chip became high vicosity chip via strong-country polycondensa-tion, the spining parameters have been set and optimized in step with the results, which have been received by means of viscosi-ty meter, automatic titrimeter, moisture meter, differential scanning calorimetry and thermogravimetric ana-lyzer. kinds of phosphorus-based totally flame retardant polyester business yarn have been developed. the draw-ing capacity, physical houses and flame retardance were studied. the results imply that the max drawingratio of the former is five.four, the latter is 6.15, the breaking tenacity of the previous is 5.28 cn/dtex, the latter is 7.03 cn/dtex, the limit oxygen index of the previous is 28.5%, the latter is 30%. with a long time storing, thespinnability of phosphorus-based totally flame retardant polyester chip and physical properties of the fiber pre-pared by way of it become awful, however its flame retardance is maintaining appropriate.