Experimental Studies of a 1Ton/Day coal slurry feed type oxygen blown, entrained flow gasifier have been performed with the slurry concentration and gasifier temperature at 65% and above 1,300 ℃, respectively. The characteristics of ash fusion temperature with addition of CaO as a flux were investigated to maintain the proper slag tapping condition in the range of reaction temperature. As the flux addition increased, ash fusion temperature showed a eutectic effect with the eutectic at around 20-30% CaO. In order to analyze the gasification characteristics, the effects of O2/coal feed ratio on the product gas composition, heating value, gasifier temperature and cold as efficiency were evaluated. From the results, it was shown in the case of Kideco coal that the cold gas efficiency was 44-60% and the heating value was 1,700-2,200 kcal/Nm(3), while Drayton coal showed a cold gas efficiency of 55-62% and a heating value of 1,800-2,200 kcal/Nm(3). In the case of Datong coal, the cold gas efficiency was 38-65%, and the heating value was 2,000-2,300 kcal/Nm(3). Also, the results showed that the optimal operating condition of O2/coal ratio for the three different coals was 0.9.