Novel CaTiO3 microspheres composed of nanosheets have been successfully prepared via a very simple solvothermal process in ethanol aqueous solution without any template or surfactant. The microstructure and morphology are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The effects of the reaction time, reaction temperature, and molar ratio of ethanol/water on the formation of the spherical structure have been investigated. CaTiO3 microspheres assembled by nanosheet units have been obtained by controlling the molar ratio of water/ethanol. The growth mechanism has been proposed based on the results of time-dependent experiments. It is proposed that amorphous particles transformed to nanosheets, and nanosheets self assembly into solid microspheres, then nanosheets building units further oriented growth along [1 1 0] direction result in the formation of nanosheets building units, and finally form the microsphere composed of nanosheets. CaTiO3 microspheres show higher photocatalytic activity than randomly aggregated nanosheets. In addition, CaTiO3 microspheres are stable during the photocatalytic reaction and more convenient to store and handle as a micrometre-scale structure. (C) 2015 Elsevier B.V. All rights reserved.