Abstract：Al2O3-coated nano-ZnO composite powder was obtained by coating precursor in slurry of basic zinc carbonate. The composite powder was examined by UV-VIS and TEM, and its photocatalytic activity was determined by photooxidation of castor oil illuminated under a high pressure mercury lamp. The composite particles are about 50 nm, and coated homogeneous film is 3~5 nm thick. The composite powder has nice ultraviolet- adsorption as good as un-coated nano-ZnO and its photocatalytic activity is reduced significantly. Compared with coating the calcined product ZnO powder surface, less steps are required in this coating process. As a result, the agglomeration during preparation steps is avoided.