The invention discloses a long-casing-pipe automatic line threading device, in order to mainly solve the problems that an existing line threading tool is time-consuming and labor-consuming and is inconvenient to use. The long-casing-pipe automatic line threading device is characterized in that a DC (direct current) motor, a circuit board (5) and a battery are fixed in a main body (1); the main body (1) is internally provided with a gear chamber (7) and a rolling wheel installation frame (8); the gear chamber (7) is internally provided with a large fluted disc (9), a reversing shaft (10) as well as a driving shaft (11) penetrating through the gear chamber; two ends of the reversing shaft (10) are respectively connected with an intermediate bevel gear (12); a driving shaft (11) is provided with an output bevel gear (13); the side wall of the main body (1) is provided with a through groove (19) along the direction of a busbar; and a wheel body in a rolling wheel assembly (17) is positioned in the through groove (19). The long-casing-pipe automatic line threading device draws a flexible conductor by adopting an electric vehicle body, and has the characteristics of time and labor saving, convenience in use and high line threading efficiency.