A series of alumina-aluminum borate (AAB) catalysts with various Al/B ratios were prepared with the coprecipitation method. The surface acidic properties of these catalysts were examined by temperature-programmed-desorption (TPD) of ammonia and the dehydration reaction of isopropanol. The dehydration reaction was carried out in a continuous-flow microreactor at 160-degrees-C under atmospheric pressure. The results of TPD of ammonia indicated that the surface acidity of AAB is medium-strong. The acidic strengths are approximately the same for all the samples. However, the acid concentration is increased with increasing the boron content of the catalyst. The dehydration activities of these catalysts are increased with increasing the boron contents of the samples. The results indicated that the addition of boron even in a small amount could significantly enhance the acidities of the catalysts.