Torrefaction process, which is one of mild pyrolysis treatment for waste biomass, is carried out around 200~300℃ to improve energy density of biomass. This paper investigates suitability of torrefied material using rice straw for coal fired power plant. by comparison of torrefaction reaction characteristic with respect to reaction temperature and residence time. The optimized torrefaction reaction condition to produce fuel from rice straw is 250℃for 20min in this study. We obtained 64.7% of fuel yield with 4,458 kcal/kg of calorific value. From the results, the characteristic of torrefaction reaction using rice straw will contribute to design pilot scale system and adjust various biomass waste materials.