The invention relates to a method and a system for evaluating the peak load regulation capacity of a single gas generator set. The method takes gas supply of the gas generator set into account, the method for evaluating the peak load regulation capacity of the single gas generator set under the condition that natural gas is in short supply is provided, and effective support is provided for power grid and gas grid cooperative scheduling. According to the method, through iterative computation, whether the gas supply of the single generator set is sufficient or not can be quickly judged, the maximum generating capacity operation mode of the generator set when the gas supply is in short supply is given out, and the peak load regulation capacity of the single gas generator set is computed. The method is in close contact with the actual motion mode of an electric power system, and has extremely high applicability.