The invention provides a rapid peak shaving method for a power grid with participation of a thermal power generating unit. The rapid peak shaving method for a power grid is provided through analysis of the operation state and the peak shaving response speed of the thermal power generating unit. The rapid peak shaving method comprises the steps of: determining the running state of a thermal power generating unit in a region; for different operation states, determining the peak shaving response speed of the thermal power generating unit to obtain a continuously updated peak shaving response speed matrix of the unit participating in peak shaving in the region; obtaining the operating load correlation matrix of the unit according to the current operation load unit participating in peak shaving; and performing peak shaving task distribution according to the operating load of the current thermal power generating unit. The rapid peak shaving method provides a much rapider and more reliable power grid peak shaving scheme by distinguishing the operation state and the peak shaving response speed of the thermal power generating unit.