Abstract: This is an article in the field of mining engineering. In view of the concentration and enrichment of lithium ions in old halide in Qerhan Salt Lake, the expansion experiment of the multi-stage precision control process of old halide enrichment was completed by means of evaporation crystallization and step separation. The enrichment law of lithium and boron during evaporation was studied. The concentration of lithium ions reached more than 1 g/L, and high quality hydrochloromagnite was obtained. The material balance of the evaporation process of the salt pan was carried out, and the actual halogen yield and lithium yield of each phase of salt extraction were obtained, as well as the production capacity of the sun salt pan and the area distribution ratio of each level of the salt pan, which can provide reliable data support for the comprehensive development and utilization of potassium old brine extraction in Qerhan Salt Lake in the future.