High purity molten salt grade potassium nitrate was prepared by the reaction of nitric acid and potassium chloride self-produced by Qinghai salt lake industry Co.,Ltd.（referred to as “Company”）.The solid phase obtained by reaction crystallization of highpurity molten salt grade potassium nitrate was potassium nitrate product.The hydrochloric acid produced by the reaction was separated from the excess nitric acid in the filtered mother liquor by extraction.Nitric acid was extracted first,and the extracted dilute nitric acid could be reused as a raw material by reaction with potassium chloride.Extracted hydrochloric acid as a by-product could be used as a raw material in other units within the Company.It could not only reduce the production costs of the enterprise,but also protect the environment and could create greater economic benefits for the enterprise.