The invention discloses a method for maintaining a graphic file of a power system off line. The method comprises the following steps: (1) defining a primitive; (2) loading the graphic file; (3) establishing a primitive object and displaying a graphic picture: dynamically loading a required primitive file from a primitive warehouse according to the primitive attribute, locally caching the primitive file, dynamically generating a corresponding primitive object in the cached information, drawing a complete graph according to the primitive attribute in a memory pool, coloring with a corresponding voltage class color according to the attribute of the voltage class; (4) performing graphic maintenance and panoramic storage: selecting the primitive object from the memory pool, instantiating the specific primitive object according to the factory class, selecting a required position according to a user demand, modifying the primitive attribute, defining an equipment name in a database, editing a graph, and saving the primitive attribute into the graphic file with a CIM/G format. Under an environment separated from an intelligent power grid dispatching control system, the method is universal and effective by meeting requirements for editing and maintaining a CIM/G file.