An ultrasonication-assisted successive ionic layer adsorption and reaction (SILAR) strategy was developed to uniformly deposit high density p-type Bi2O3 quantum dots on n-type TiO2 nanotube arrays (Bi2O3@TiO2 NTAs), which were constructed by electrochemical anodizing in ethylene glycol containing electrolyte. Compared with pristine TiO2 NTAs, the Bi2O3 quantum dots sensitized TiO2 NTAs exhibited highly efficient photocatalytic degradation of methyl orange (MO). The kinetic constant of Bi2O3@TiO2 NTAs prepared by an ultrasonication-assisted SILAR process of 4 cycles was 1.95 times higher than that of the pristine TiO2 NTAs counterpart. The highly efficient photocatalytic activity is attributed to the synergistic effect between the formation of uniform p-n heterojunction with a high-density for enhancing light absorption and facilitating photogenerated electron-hole separation/transfer. The results suggest that Bi2O3/TiO2 p-n heterojunction nanotube arrays are very promising for enhancing the photocatalytic activity and open up a promising strategy to design and construct high efficiency heterogeneous semiconductor photocatalysts.