The relevance of the work is caused by the need to reduce the labor intensity of electrical design drawings in the instrument as well as by the quality improvement of the design documentation and the need to prevent discrepancies between the table of compounds, a table of contacts and pictures of wiring harness layout. The main aim of the study is to review the basic questions of application development for the automatic modeling of assembly and switching space, to identify the basic principles of the software structure. Methods: object-oriented and structured programming techniques; search methods on graphs; installation and switching space modeling technique; application of DBX interface for reading netlist data of the active project P-CAD 2006 Schematic, SQLite databases for storing information about the types of connectors and cables; the QT library while designing the application interface. Results. The authors have developed the software for automatic modeling of assembly and switching space. The software features: - CAD-independent input, storage, graphical display of circuitry data; - input data control; - automated receiving of connections tables and electrical circuit contacts; - interactive and automatic wiring harness; - mapping of the diameter, length and number of wires at any point of the routed harness segment; - reporting on data structures current state; - wiring drawings export. The paper introduces a series of algorithms which allow automating data loading circuitry of the system P-CAD 2006 Schematic. The authors proposed the algorithm for determining states of circuits circuitry based on the Boost Graph Library, which is formed of the breadth-first search on a graph algorithm and the structures for storing information on the permitted types of connectors and wiring harness.