The invention provides an automatically generating method and device of a power plant identification system code. The method includes the following steps that according to a selected system diagram, a page is drawn, and the machine group number of a power plant identification system is determined; according to a selected graphic primitive matched with the engineering design structure of power plant equipment, a power plant identification system classification code of the graphic primitive is read; for the system diagram drawn by the graphic primitive, a power plant identification system number corresponding to the system diagram is generated; according to the machine group number of the power plant identification system, the power plant identification system classification code and the power plant identification system number, the power plant identification system code of the system diagram is generated. According to the method and the device, automatic generation and automatic labeling of the power plant identification system code of the system diagram can be achieved through a computer system, the coding error rate, the repeat code rate and the labor cost are reduced, the digital management and safety operation level of an enterprise are improved, the working efficiency is improved, unified, scientific, correct and complete power plant identification system code data is provided for the application of the method and the device, and the integrated cost of the enterprise is largely reduced.