Since there are many similarities in the catalytic properties between carbides and noble metals, the study of carbides has become one of the research fields in catalysis[1,2]. Mo2C is typical of carbides, and α-MoC1-x and β-Mo2C with high specific surface area are often used as catalysts for hydrogenation, dehydrogenation, etc[1～6]. But the used α-MoC1-x and β-Mo2C are usually prepared under different conditions[3,5,6], which might lead to the differences in some physical properties (e.g. specific surface area and size of the crystalline) between the two molybdenum carbides. In these cases, the comparison of the real activity of the two carbides is difficult. Aromatization of lower alkanes could be catalyzed by Mo/HZSM-5 and it was suggested that Mo2C/HZSM-5 is an active catalyst[7,8]. When studying aromatization of n-butane over Mo/HZSM-5, we found that α-MoC1-x and β-Mo2C supported on HZSM-5 could be prepared under similar conditions.rn