Developing integrated coal gasification combined cycle systems ensures that Japan will have cost-effective and environmentally sound options for supplying future power generation needs. The reduction of NOx emissions and increasing the inlet temperature of gas turbines are the most significant issues in gas turbine development in IGCC. The coal gasified fuel, which is produced in a coal gasifier of air-blown entrained-flow type has calorific value as low as 1/10 of natural gas. Furthermore the fuel gas contains ammonia when a gas cleaning system is a hottype, and ammonia will be converted to nitrogen oxides in the combustion process of a gas turbine. The study is performed in 1300 °C-class gas turbine combustor firing coal-gasified fuel in IGCC power generation systems. In the previous study° the advanced rich-lean combustor of 150-MW class gas turbine was designed to hold stable combustion burning low-Btu gas fuel and to reduce fuel NOx emission that is produced from the ammonia in the fuel. By testing it under atmospheric pressure conditions, we have studied the effects of fuel parameters on combustor performances and listed the basic data for development applications. In this study, by testing it under pressurized conditions, we have obtained a very significant result through investigating the effect of pressure on combustion characteristics and wish to provide herein a summary of our findings.