Generation facilities in Korea have been allocated to six firms as a part of restructuring and there is a competitive bidding in the wholesale market, albeit strictly on a cost basis. And Korean government has developed "Basic Plan of Long Term Electricity Supply & Demand" in order to secure resource adequacy. Addition of new generation capacities has controlled by this plan. However, if the restructuring will be complete done, generation companies have no obligation to invest if their profitability is not guaranteed. Many experts are arguing that government intervention is still necessary to avoid the price spike in the wholesale market. In this study, simulations for two scenarios were conducted to see whether competition market can help to stabilize the wholesale price in Korean market. The simulation results show that government intervention can prevent the price spike. However, the wholesale price in the competition market turns out to be lower than that in the regulated market due to the more new investment. However, this model has many limitations. First of all, this model assumed that only gas power plants can respond the market price.