Abstract: A carbon-based solid acid catalyst(H-Al/AC) containing Brønsted(B) acid and Lewis(L) acid was prepared by H₂SO₄ sulfonation and AlCl₃ immersion using coconut shell activated carbon(AC) as carrier. This catalyst was used to prepare 5-hydroxymethylfurfural(5-HMF) from glucose in a biphasic system(water/2-sec-butylphenol) by hydrothermal rection. The catalyst was characterized by SEM, BET, XRD, NH₃-TPD and pyridine infrared to investigate the influence of preparation conditions on the structure and activity of the catalyst. The results showed that the catalyst activity reached the highest after being sulfonated with 98% H₂SO₄ and immersed in saturated AlCl₃ solution for 4 h. The catalyst showed an amorphous carbon structure with the specific surface area of 1 139.31 m²/g, B acid amount 4.213 μmol/g and L acid amount 29.97 μmol/g, respectively. The catalytic performance of the prepared catalyst was investigated for the conversion of glucose to 5-HMF in biphasic system when the ratio of aqueous phase to organic phase was 1:2, and the results showed that the highest 5-HMF yield of 25.14% were obtained at 180℃ for 210 min with 0.025 g of catalyst. The reaction path of glucose conversion to 5-HMF was as follows: glucose was isomerized into fructose under the action of Lewis acid in the aqueous phase. Fructose was dehydrated under the catalysis of Brønsted acid to generate 5-HMF. 5-HMF was extracted into 2-sec-butylphenol(SBP), and the generated water was retained in the aqueous phase. The catalyst cycle stability test showed that the activity of the catalyst was 86% of the initial activity after repeated use for five times.