Abstract Anatase titanium dioxide (TiO2) microspheres with high photocatalytic activity were prepared by a novel pyrolysis method using titanium sulfate powders as the precursor. The photocatalytic activity of the as-obtained anatase TiO2 microspheres was evaluated by degrading rhodamine B (RhB, 20mg/L) and 4-nitrophenol (4-NP, 10mg/L) under UV-light irradiation at room temperature. A possible mechanism for the formation of the TiO2 microspheres was proposed. The effects of calcination temperature and time on the morphologies and photocatalytic activities of the TiO2 microspheres were studied. It was found that the anatase TiO2 microspheres can be obtained above 600°C. The nucleation of primary TiO2 particles stemmed from the rapid pyrolysis of titanium sulfate powders, followed by the aggregation and recrystallization, resulting in the formation of the anatase TiO2 microspheres. With increasing the calcination temperature from 600 to 900°C, the crystallinity and pore size of the TiO2 microspheres increased and their specific surface areas decreased. The experimental results indicate that the crystallinity and specific surface area of the TiO2 microspheres have significant effects on their photocatalytic activities. The as-synthesized TiO2 microspheres obtained at 700°C for 6h exhibited the highest photocatalytic activity and good stability.