The goals to enhance the efficiency and environmental friendliness of power plants burning fossil coal explain the interests in the technologies of gasification in the combined cycle (IGCC). The research is dedicated to a promising IGCC process flow diagram which suggests an intermediate overheating of the cycle air coming to the combustion chamber of the combined cycle plant. After air processor the air goes to the boiler where it is heated to the temperature of 1000° C. Compared to the classical IGCC plants, the air overheating makes it possible to reduce the capacity of gasifier and gas cleaning system. The plant flow diagram also includes a two-stage MHI gasifier. The gasifier is fed by overheated cycle air, steam and oxygen from the air separation unit. In the research the operating conditions of gasifier and the whole plant are studied. The efficiency of electricity generation without considering auxiliaries reaches 53-54.4%. The hot gas cleaning and oxygen steam gasification is optimal.