Abstract: There are a series of problems restricting the development of an ultralow magnetite concentrator in Hebei Province， such as the poor effect of waste discarding in dry dressing on-site process， the low grade of ore entering grinding system， the high cost of grinding system， and the large amount of wet tailings to be sent to the tailings pond. In order to solve these problems， the suspension dry pre-separation （instead of magnetic pulley dry separation） - high pressure grinding roll - suspension dry re-election test for fine crushed products was carried out. On the basis of good results obtained from the test， the on-site technological process was reformed: Expanding the capacity of the rough， medium and fine crushing system is three times that of the original. The magnetic pulley dry separation of fine crushing products is transformed into the suspension dry pre-separation， and the high pressure grinding roll-suspension dry re-separation system for dry pre-concentration concentrate is added. The linear vibrating screen， which was accompanyed with ball mill to form closed circuit， was transformed into a cyclone group. The comparison results before and after the transformations are as follows. After the transformation， the amount of minerals entering the grinding system is greatly reduced to 16.70%， and the grain yield of the grinding system to the ore -0.074， -1 mm is increased by 15.54 and 32.97 percentage points， respectively. The grindability of the ore is significantly improved，the magnetic iron content is greatly increased to 28.32%. The magnetic iron content of dry throwing tailings is obviously lower than that before the transformation. Although the content of -0.074 mm in the concentrate decreases from 75% to 67%， the grade of the concentrate increased by 2.18 percentage points， that’s 65.66% compared with that before the transformation. The new process fully exerts the selective crushing effect of the high pressure grinding roll and the high-efficiency enrichment ability of the suspended dry sorter， which greatly reduces the grinding energy consumption， wet tailings yield rate， and the argillization of the gangue， the water consumption per ton of ore. In addition， the new process improves the sorting effect and the final concentrate grade， and extends the service life of the tailings pond.

Key words: High pressure grinding roll, Ultralow magnetite ore, Suspension dry separator, Dry throwing tail