Herein we studied the characterization of the PBO films formed via solution casting and thermal cyclization of poly(o-hyroxyamide)s(PHAs) that were synthesized by direct polycondensation of 3,3'-dihydroxybenzidine with 4,4'-(2,3-quinoxalinedioxy) dibenzoic acid and/or 4,4'-(2,3-pyridinedioxy) dibenzoic acid. All the PHAs exhibited inherent viscosities in the range of 0.55~0.84 dL/g in DMAc solution. The copolymers, CPH-2-5, were partially soluble in less polar solvents like pyridine and THF. However, all the PBOs were not soluble in polar solvents, but only partially soluble in sulfuric acid. The temperatures corresponding to 10% weight loss of the PBOs with increasing content of quinoxalinedioxy unit were higher than those of the PHAs, and the char yields at $900^{\circ}C$ in $N_2$, tensile strength, and initial modulus of the PBOs were 1.1~1.3 times, 1.2~1.8, and 1.6~3.3 times higher, respectively, than those of the PHAs. The LOI value of CPB-2 was 38.5%, while that of CPB-1 was the highest at 40.0%. The LOI test confirmed that excellent flame retardants were synthesized.