Abstract: In order to effectively develop and utilize the increasingly depleted magnetite resources and deal with the problems of high energy consumption and high cost of traditional beneficiation process，a typical lean magnetite ore in Benxi is taken as the research object，and the process optimization test of large dry preconcentration-high pressure roller mill crushing-wet coarse preconcentration is carried out. The effects of three core process parameters of dry pre-separation magnetic field intensity，high pressure roller mill closed-circuit screening particle size and wet pre-separation magnetic field intensity on the sep⁃ aration index are investigated systematically.The results show that the CTDG 0604 dry magnetic separator is used for dry preconcentration and tailing discarding under the magnetic field strength of 437.69 kA/m. The dry-discarded concentrate is crushed by GM100/30 high-pressure roller mill under the condition of 3 mm closed circuit. The high-pressure roller mill product is then subjected to secondary preconcentration by CTB 0403 wet magnetic separator under the magnetic field strength of 238.74 kA/m.Under this optimal process flow，the total tailing discarding rate of 65.45% can be achieved before the ore enters the final grinding，of which the dry discarding rate is 23.51% and the wet discarding rate is 41.94%. The iron grade of the grinding material is significantly increased from 16.48% to 44.87%，and the iron recovery rate is as high as 93.97%.The energy-saving process flow constructed in this study realizes the“throwing waste as early as possible”of gangue minerals，which can provide technical path and engineering reference for the efficient and green development of low-grade magnetite of the same type.

Key words: lean magnetite, dry preconcentration, high pressure roller mill, wet magnetic separation, tailings discarding