The invention relates to an automatic control method of 300MW grade circulating fluid bed unit, which sets the automatic control methods for the coordination of machine and furnace, the deviation of single bed pressure and double bed pressure, the water level of the deaerator and the condenser, the secondary air quantity/oxygen quantity and the secondary air pressure, the boiler bed temperature, the fuel flow and the limerock feeding during making the first 300 MW circulating fluid bed unit as the localization of manufactures, meanwhile, the 300 MW circulating fluid bed unit has the advantages of stable operation, safety, reliable and remarkable economic operation passing through the coordination and control for the system.