Al2O3 and SnO2 mixed oxide were obtained by the coprecipitation method at different Sn4+ contents, from the urea hydrolysis at 95 degrees C using nitrate salt as metal precursor. The studies of X-ray diffraction and reflectance diffuse UV-Vis spectroscopies and N2 adsorption-desorption show important changes. The photocatalytic efficiency test for the mineralization of phenol was determined from UV-Vis spectroscopy. The Al2O3-SnO2 mixed oxide with 10% mol of Sn4+ improved the photocatalytic activity in the elimination of phenol under UV light irradiation, where the photodegradation rate was 2 times more active than Al2O3 unmodified and 1.4 times more active than the reference photocatalyst TiO2-P25. The high activity observed was discussed as a function of the small particle size of SnO2.