A series of Al-SBA-15 materials with different Si/Al ratios have been prepared via a post-alumination procedure. The results show that Al species can be introduced into the SBA-15 framework. Only the medium acid sites can be observed on the Al-SBA-15 samples, and the number of acid sites decreases with the increase of the Si/Al ratio. The hydroisomerization activities of n-dodecane over 1% Pt/Al-SBA-15-n catalysts increase with the number of acid sites, and the largest isomers yield reaches to 51%. It suggests that the Al-SBA-15 material is a suitable acid component for bifunctional catalysts for hydroisomerization of long chain n-paraffins.