Abstract: Based on the working principle and product characteristics of High Pressure Grinding Rolls (HPGR)，the role of ultra-finely crushing by HPGR in the process of lean magnetite ore crushing were analyzed. The special laminating and crushing method of HPGR makes the crushed product have the characteristics of high content of fine-grained particles, sufficient development of micro-cracks and good dissociation characteristics. Ultra-finely crushing by HPGR - pre-concentration process can throw a large amount of tailings to improve the grade before lean magnetite ore enter into the mill. The efficiency of separation is improved by reducing the amount of grinding and reducing the Bond work index of ore, which is conducive to energy saving. In the future, the adaptability of HPGR equipment to ore properties and production process should be strengthened, a new type of HPGR equipment with high efficiency and low consumption should be developed. The process has better indicators when HPGR was used in conjunction with advanced pre-concentration equipment. The development of matching advanced pre-concentration equipment for the characteristics of HPGR products which have great significance for improving the index of ultra-finely crushing by HPGR - pre-concentration process.

Key words: High Pressure Grinding Rolls, Ultra-finely crushing, Lean iron ore, Pre-concentration