The invention relates to a method for the external refining purification of industrial silicon. According to the method, refining gas is continuously introduced into a two-man ladle before industrial silicon melt is released into the two-man ladle from a submerged-arc furnace, and the silicon melt is then released into the two-man ladle for being subjected to external refining. The industrial silicon melt in the two-man ladle is heated by an external plasma heating device, the external refining temperature for the industrial silicon melt is enabled to be controlled in a certain range, and a refining agent is added into the two-man ladle so as to carry out slagging refinement. Through the external refining process, most metallic impurities, including Al, Ca, Ti, Na and Mg, and partial non-metallic impurity impurities, including B, P, S and C, can be removed from the industrial silicon melt, so that the quality of industrial silicon products is effectively improved, and high-quality industrial silicon products with low boron, phosphorus and metallic impurity content are obtained. The method has the characteristics of full energy utilization and conservation, high production efficiency, less investment in capital construction, no environmental pollution, and the like.