A series of polyester-amides that contain phosphorus were synthesized by low temperature solution condensation of 1,4-bis(3-aminobenzoyloxy)-2-(6-oxido-6H-diben[c,e][1,2]oxaphosphorin-6-yl) phenylene (III) with various aromatic acid chlorides in N-methyl pyrrolidone (NMP). All polyester-amides are amorphous and readily soluble in many organic solvents such as dimethylacetamide (DMAc), NMP, dimethylsulfoxide, and dimethylformamide at room temperature or on heating. Light yellow and flexible films of these polyester-amides could be cast from the DMAc solutions. The polymers with an inherent viscosity of 0.26-0.72 dL/g were obtained in quantitative yields. These polyester-amides have good mechanical properties (G＇ of similar to 10(9) Pa up to 200 degrees C) and good thermal and flame retardant properties. The glass transition temperatures of these polyester-amides ranged from 250 to 273 degrees C. The degradation temperatures (T-d 5%) in nitrogen ranged from 466 to 478 degrees C and the char yields at 800 degrees C were 59.6-65.2%. The Limiting oxygen indexes of these polyester-amides ranged from 35 to 43.