In order to improve the thermal efficiency of the oxygen-blown integrated gasification combined cycle (IGCC) and to meet stricter environmental restrictions among cost-effective options, a hot/dry synthetic gas cleanup is one of the most hopeful choices. The flame temperature of medium-Btu gasified fuel used in this system is high so that formation by nitrogen fixation results to increase significantly. Additionally, the gasified fuel contains nitrogenous compound, as ammonia, and it produces nitrogen oxides, the fuel , in the case of employing the hot/dry gas cleanup. Low combustion technology to reduce both fuel- and thermal- emissions has been required to protect the environment and ensure low cost operations for all kinds of oxygen-blown IGCC. In this paper, we have demonstrated the effectiveness of two-stage combustion and nitrogen injection techniques, and also showed engineering guidelines for the low- combustor design of oxygen-blown gasified, medium-Btu fuels. The main results obtained are as follows: (1) Based on the basic combustion tests using a small diffusion burner, we clarified that the equivalence ratio at the primary combustion zone has to be adjusted according to the fuel conditions, such as methane concentration, molar ratio, and calorific values of gasified fuels in the case of the two-stage combustion method for reducing fuel- emissions. (2) From the combustion tests of the medium-Btu fueled combustor, two-stage combustion with nitrogen direct injection into the combustor results in reductions of emissions to (corrected at 16% ) or less under the gas turbine operational conditions of 25% load or higher for IGCC in the case where the gasified fuel contains 0.1% methane and of ammonia. Through nitrogen direct injection, the thermal efficiency of the plant improved by approximately 0.3% (absolute), compared with the case where nitrogen was premixed with gasified fuel. The emission concentration decreased drastically, as low as , or combustion efficiency was kept higher than 99.9%. The above results have shown that a two-stage combustion method with nitrogen direct injection is very effective for reducing both fuel- and thermal- emissions at once in IGCC, and it shows the bright prospects for low and stable combustion technology of medium-Btu fuel.