Poly(amide-imide)s (PAIs) were synthesized from 9,9'-bis(4-aminophenyl)fluorene (APF) and different diimide-dicarboxylic acids (DIDA). The aromatic fluorene group is isolated by DIDA. The structure of the polymer was confirmed by H-1 NMR, C-13 NMR, and FTIR. These PAIs were soluble in polar aprotic solvents, such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide. The crystallinity of the polymers is estimated by means of wide-angle X-ray diffraction. The resultant PAIs exhibited nearly amorphous nature. Thermal stability of the PAIs was characterized by differential scanning calorimetry and thermogravimetric analysis. No obvious glass transition temperatures were detected and the 5 % weight loss temperatures of the PAIs were in the range 296-453 degrees C in nitrogen. The optical properties were studied by Ultraviolet-visible (UV/VIS) spectra and photoluminescent (PL) in solution and film states. The results show similar absorbance and emission to those of the constituting APF monomer. The highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) were estimated from cyclic voltammograms. The values of HOMO and LUMO are -6.67 to -6.72, and -3.54 to -3.58, respectively. Their optical and electrochemical properties are not changed significantly by different DIDA.