The invention discloses a control method for a supercritical unit participating in primary frequency regulation and a control system model. The method comprises the following steps: when the supercritical unit operates steadily under a given working condition, an intermediate pressure regulation valve is fully opened, and a high pressure regulation valve is regulated to a preset opening; when loadof the unit is increased, the opening of the high pressure regulation valve is increased, and the opening of the intermediate pressure regulation valve remains unchanged; when reduction of the load results in increasing of a power grid frequency, the opening of the high pressure regulation valve and the opening of the intermediate pressure regulation valve are reduced at the same time, and the high pressure regulation valve and the intermediate pressure regulation valve participate in primary frequency regulation at the same time; and after regulation, the intermediate pressure regulation valve is regulated to be in a full opening state. The high pressure regulation valve and the intermediate pressure regulation valve of a reheat turbine unit can participate in power grid primary frequency regulation at the same time, and the supercritical unit primary frequency regulation ability can be improved.