A novel three dimensional (3D) self-assembled hierarchical bismuth oxide was prepared via a sol-gel synthesis with the aid of capping agent of polyethylene glycol-8000 (PEG-8000) at 85 ℃ in 45 min. The morphology evolution was studied versus reaction time and interpreted in terms of growth mechanisms. The as-grown 3D hierarchical flower-like bismuth oxide was crystalline cubic gamma-phase. The morphology and crystal phase of these 3D cubic gamma-phase bismuth oxide flowers were not changed with heating up to 600 ℃. The flower-like morphology was attributed to modification of the growth kinetics by the capping agent from the PEG-OH bond bridging with bismuth ions. Europium doped gadolinium oxide shell were further deposited on the bismuth oxide cores through sol-gel synthesis showing good photoluminescence characteristics at 610 and 622 nm under the excitation at 280 nm.