A series of new polyfluorenes with dendritic functional cabazole and oxazole side chains have been successfully designed, synthesized, and characterized. These copolymers show good thermal properties and solubility in organic solvents, such as THF, CH2Cl2, CHCl3, toluene, etc. The photoluminescent (PL) and electroluminescent (EL) emission color quality was improved very much due to less aggregates of main chains of polyfluorenes (PFs) with the steric hindrance of dendritic functional carbazole and oxazole units. The electroluminescent devices based oil these copolymers as blue emitters and host materilas were fabricated and evaluated. Balanced carriers and high efficiencies were obtained in both nonphosphorescent and phosphorescent PLEDs. The best devices were obtained by using PFCO1 materilas with the exteral quantum efficiencies of 1.03% for ITO/PEDOT/PFCO1/TPBI/LiF/Al and 11.63% for ITO/PEDOT/PFCO1:(tpbi)(2)-Ir(acac)/Ca/Al. The results indicated that these copolymers were promising candicates for both efficient pure blue emitters and host materials for highly efficient phosphorescent PLEDs.