Novel poly[(fluorene)-co-(2,8-dioctyldibenzothiophene-S,S-dioxide-3,7-diyl)]s were synthesized. The octyl group on the 2,8-dioctyldibenzothiophene-S,S-dioxide (DOSO) unit improved the solubility of the polymers and broadened the optical band gap from 2.95 to 3.20 eV as the content of DOSO unit increases. The electroluminescence (EL) spectra of polymers show CIE coordinates around (0.16, 0.07) independent of the ratio of DOSO units in the polymers, owing to the ICT and steric hindrance dual-function. A high efficiency of 3.1 cd.A(-1) (EOE = 3.9%) was obtained with the configuration of ITO/PEDOT:PSS/polymer/Ba/Al. The results indicate that PF-3,7DOSOs could be a promising candidate for saturated blue-emitting polymers with spectral stability and high efficiency.