The invention discloses a transformer substation electrical secondary circuit connection relation method and system based on CAD drawing automatic pickup and a medium.. The method comprises the following steps that an element identification primitive library is established; various secondary elements in a CAD drawing are automatically identified; various attributes of the secondary elements are identified, connecting lines in the CAD drawing are identified, loop description function description textboxes are identified and the like, so that the substation electrical secondary loop connectionrelationship in the CAD drawing is automatically identified, and a corresponding secondary loop standard file can be output as required. The problems that the digitalized workload of the CAD drawing of the stock electrical secondary circuit of the transformer substation is large, the correctness of the digitalized drawing cannot be guaranteed and the digitalized period is long can be effectively solved; a transformer substation can be effectively supported to carry out digital design work, and meanwhile support is provided for advanced application of an electrical secondary circuit according to a model file output by a digitalized CAD drawing.