Two game theory models,Cournot and Stackelberg,and the analyzing way of investing option for two competing corporations are introduced to find the optimal strategies of pure and mix Nash equilibriums.With the mathematic simulation,the market dominant investment decisions for corporations with or without monopolistic investment opportunity under different market conditions are analysed and the influence of market fluctuation on investment decision making is discussed.When facing serious market competition,corporations usually expect to foster and develop core competency by market dominant investment to prevail in the competition and gain a bigger market share in the future.However,because of the market uncertainty,making investment decision can bring to corporations loss or benefit,therefore,how to make market dominant investment decision is absolutely what corporations should focus.