Korea has introduced power trading system since 2001 but long-term Generation system planning has been executed by government for cost minimization every 2 years. Until currently the model which is used for generation system planning and best-mix only considers cost minimization and total yearly or quarterly electricity demand every year. In a view point of one day power supply operation, the ramp up/down rate of total generation system, minimum up/down time and GFRQ(Governor Free Response Quantity) are very important. This paper analyzes optimal fuel-mix for 2022 Korea generation system satisfying these constraints of each fuel type and considering pump storage plants, construction cost and $CO_2$ Charge Using MILP(Mixed Integer Linear Programming) method. Also the sensitivity analysis which follows in future power industry environmental change accomplished.