Aluminum ion-exchanged Ca-montmorillonite with different concentrations of aluminum ion were prepared and applied in the conversion of carbohydrates to 5-hydroxymethylfurfural (HMF). It was found that two types of acid sites were present in the catalyst, Lewis acid sites for isomerization of glucose and Bronsted acid sites for dehydration of fructose. With Al-mont-10 as catalyst, the yield of HMF converted from glucose was 80.4% in a biphase system (THF: NaCl solution) at 180 degrees C for 2.5 h. Further, the catalyst also shows excellent catalytic performance in the conversion of starch and inulin, and the yield of HMF reached 60.1% and 81.6% under identical conditions, respectively.