This study discusses the generation expansion planning under a $CO_2$ emission regulation which is expected to affect much not only energy demand and supply, but economy. In order to find out the generation expansion planning, the Multi-criteria generation expansion planning model is used for a capacity expansion planning tool, and converted into a form for conforming to annual $CO_2$ emission regulation. This study reflacts the electricity efficiency improvement technologies, the fuel substitution and the electricity conservation in the generation expansion planning, in order to reduce $CO_2$ emission in a electric power supply. Through scenario studies, it is found that the integrated approach to cope with $CO_2$ emission regulation is important in generation expansion planning, and LNG and Nuclear will play a important role in coping with $CO_2$ emission regulation.
