In order to improve the adaptability and reliability for evaluation of the investment value of power plant carbon capture systems，a decision-making mathematical model for carbon-capture system optimal investment timing is proposed based on the real option theory by referring to the real option characteristics of venture capital investment for carbon capture systems.By taking into account the irreversibility and delay ability of investment decisions，and the uncertainties of carbon price and carbon mitigation cost，the investment critical value and the optimal investment strategy for power plant carbon capture systems are obtained.The results of numerical example reveal that the model can make a rational assessment for the opportunity cost of venture capital investment，and the potential value of the project can be exploited as much as possible.Compared with the traditional net present value assessment method，the proposed model can overcome the defects of the net present value method，and effectively guide the timing of carbon capture system risk investment，rather than make the simple decision on immediate investment or nondevelopment.The model has provided a quantitatively analytic mathematical tool for the investment carbon capture system in a power plant that can be used as scientific reference for decision-makers.