The invention relates to a method for large-scale production of continuous carbon nano tube fiber. The carbon nano tube fiber is continuously prepared by connecting multiple furnaces in series, utilizing airflow in multiple times, and simultaneously stabilizing multiple furnaces. The mixed reaction solution of an ethyl alcohol carbon source, a ferrocene catalyst, a thiophene accelerant and a water assistant is injected by utilizing a micro-injection pump, and guided to a first hydrogen flow furnace via a nozzle, a cylindrical continuous carbon nano tube aggregate is generated at a reaction zone, and the continuous carbon nano tube fiber is obtained via mechanical traction, waterlogged densification and twining by an external spindle; the airflow is guided to a rear furnace once more via a transmission device, the same reaction solution is injected, the hydrogen flow rate and the solution injection speed of the rear furnace are regulated, the cylindrical continuous carbon nano tube aggregate is generated in the rear furnace, and the continuous carbon nano tube fiber is obtained via mechanical traction, waterlogged densification and twining by an external spindle. According to the invention, the multiple furnaces can at least simultaneously stabilize spinning to reach the hectometer level, and the obtained fiber is mainly composed of double-walled carbon nano tubes; the fiber has better degree of crystallinity, certain strength and electrical conductivity, and is similar to fiber prepared through a typical single reactor.