Abstract: In order to improve the synthesis of 4,6-diaminoresorcinol diphosphate,we prepared 4,6-(diaminoresorcinol) diphosphate by polyphosphoric acid and characterized its structure.The preparation of(4,6-)diaminoresorcinol diphosphate by PPA method reduce reaction time from two or three days to some hours and enhance the yield from 79.46% to 91.12%.To enhance the stability of 4,6-diaminoresorcinol diphosphate,H_3PO_2 was used for the stabilization of 4,6-diaminoresorcinol diphosphate.The study manifests that 4,6-diaminoresorcinol diphosphate is stable for oxidization after being placed one month.PBO spinning solution was prepared from 4,6-diaminoresorcinol diphosphate in polyphosphoric acid by solution poly-condensation.The polymerization degree of obtained PBO is high and the inherent viscosity is(17 dL/g.)