As an approach to evaluate the performance of the IGCC(Integrated Gasification Combined Cycle) PDU(Process Development Unit) process and to understand the integration conditions between coal gasification plant and gas turbine system, process simulations for 100 ton/day-class IGCC PDU plant have been carried out. Two bituminous and two subbituminous coals were selected for this study. Power output and cycle efficiency have been calculated for two gas turbines, one for M3142(J) and the other for LM1600PA of General Electric company. In addition, the process simulations based on design thermal input of both gas turbines have been conducted to calculate the power output and cycle efficiency. For the 100 ton/day-class PDU plant, simulation results exhibit that about 80 ton/day of oxygen is required while 80 ton/day of saturated steam from the raw gas cooling system and 350-450 ton/day of saturated steam from the flue gas cooling system are produced. The power output and cycle efficiency of gas turbines are 4.5-8.5MW and 22-32 % when coal gas is fried, which are fairly lower than those of natural gas firing cases. On the basis of the design thermal input of the gas turbines, the coal consumption rate is 1.3-1.8 times of the 100 ton/day-class PDU plant and the saturated steam production is increased in this proportion. The power output and efficiency of coal gas firing cycles are similar or slightly higher than those of natural gas firing cases regardless of coal type.