The invention relates to a production method of high purity silicon, including the following steps: preparing silica solution, deslagging, secondary deslagging, and directional solidification and separation; the production method of the invention solves the technical problem that the existing production method of high purity silicon has complex technical process, high energy consumption and is not suitable for large-scale industrial production, and has the advantages of simple manufacturing technique, low energy consumption, low content of impurities, high purity of high purity silicon, the elimination of the phenomena of furnace bottom rising, fast reaction speed, simple furnace structure and little modification to the existing production equipment.