Several alumina-supported molybdenum-based catalysts were prepared by impregnation. The prepared catalysts were characterized using N-2 adsorption, X-ray diffraction, temperature-programmed desorption of ammonia, and temperature-programmed reduction with hydrogen. The catalytic activity in mixed alcohol synthesis was evaluated using a fixed-bed pressurized flow reaction system under conditions of 250-320 degrees C, 3.5-5 MPa, gas hourly space velocity of 280-5000 h(-1), and H-2/CO ratio of 0.5-1. Effects of reaction conditions, alumina supports, and the addition of potassium were elucidated. The CO conversion and selectivity of the catalysts changed depending upon the calcination temperature of alumina supports that influenced the acid amount of the catalysts. The selectivity of C2+ alcohols eventually reached ca. 40% in the case of calcination temperatures higher than 1000 degrees C. The selectivity of C2+ alcohols was almost proportional to the addition of potassium that promoted the formation of C2+ The selectivity of C2+ alcohols and the chain growth probability of alcohols with potassium carbonate were higher than those with nitrate.