The morphology of the hydrous alumina coating on TiO2 particles from aqueous precipitation at different pHs and temperatures was studied, and a "phase diagram" was obtained. Al-2(SO4)(3) solution was the coating reagent, and NaOH solution was the precipitant reagent. The effect of pH and temperature on the hydrolysis of Al3+, the size and structure of the OH-Al species, and the coating morphology were investigated. Four kinds of coating morphologies were observed: dotted coating, film coating, floccule coating, and flake coating. When the pH was lower than the isoeletric point of the TiO2 particles (pH 4.1), there was dotted coating. When the pH was higher than the isoeletric point and with increasing pH and temperature, the hydrous alumina coating changed from a uniform and continuous amorphous film coating to a loose floccule coating, then to a flake coating.