Abstract: A series of random copolymers of poly(p-phenylenebenzobisoxazole)-co-poly(9,9-dioctyl fluorenol benzobisoxazole)(PBO-co-PBOF) with different PBOF content were synthesized through condensation polymerization. Xray diffraction, UV-Vis absorption and photoluminescence spectroscopy were used to study the effect of the structures on the modalities and optical properties of the copolymers. Compared with PBO, amorphous structures of the copolymers were observed with the existence of fluorene units in the main chains. The emission spectra in MSA solution were mainly dominated by PBOF with χ(PBOF)≥50%. Copolymers in films exhibited a general trend of red shift to the maximum emission with the increasing of PBOF content due to the interaction between efficient intraand/or intermolecule energy transfer and easily formed aggregate. Furthermore, compared with the spectra in DMAc solution, the protonated PBOF in MSA solution showed significant red shift in both UV-Vis absorption spectra and fluorescence emission spectra.