Nanostructured SnO2:Al powders were prepared and their electro-optical activities were regulated by using a micro drop fluidized reactor (MDFR), which were conducted continuously in a simple one-step process without additional calcination, annealing, and drying steps. The crystallite size and BET surface area (up to a 2.6 times) increased but bandgap energy of SnO2:Al powders decreased, respectively, by providing the unique pyro-hydraulic reaction conditions during the formation of powders. The micro shear force and strain generated due to the fluidization of micro drops could enhance the doping effects and surface activities of SnO2:Al powders. The analyzes of room-temperature photoluminescence (PL) spectra, UV-vis photospectroscope and X-ray photoelectron spectra (XPS) exhibited that the surface activities of SnO2:Al powders were enhanced considerably by regulating the excitation and separation of electrons and holes and increasing the oxygen vacancies at the surface of SnO2:Al powders by means of UMB control. The optimum amount of dopant of Al3+ ions (C-Al) and flow rate of micro bubbles (UMB) for effective surface activities were 2.0 at % and 1.0 L/min, respectively. The scheme of photocatalytic mechanism of SnO2:Al powders to degrade the methylene blue (MB) was discussed by means of surface charge transfer and morphology of the powders. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.