Abstract: The iron grade of feeding to coarse and fine fraction classification hydrocyclone was 32.43% in Qidashan Iron Concentrator. Some features， including obvious enrichment of iron minerals in fine fraction， the coarser cut size of coarse and fine fraction （d50=0.043 mm）， lower yield of underflow， less feeding of gravity concentration， and larger feeding of magnetic separation-reverse flotation process， led to higher production cost. Beneficiation tests were conducted with d50 of 0.036 mm， 0.025 mm and 0.020 mm respectively， in order to determine the suitable classification size of coarse and fine fraction classification. Suggestions for technological improvement were given accordingly. The results show that， with the decrease of d50， the iron grade of total concentrate decreases slightly at first and then obviously， while the yield and iron recovery increase obviously at first and then keep in a higher level， the ratio of gravity concentrate to total concentrate increases substantially. The cut size d50 should be suitable of 0.025-0.020 mm from 0.043 mm for the coarse and fine fraction classification of Qidashan Iron Concentrator. The final suggestion is that， while optimizing the d50 of coarse and fine fraction classification， fine iron minerals should be fed into magnetic separation-reverse flotation process as soon as possible by realizing the three-product model of the roughing spiral. Medium intensity magnetic separation for tailings discarding should be abolished， to improve the liberation degree and recovery of iron minerals. In the recommended process， the advantage of gravity concentration process is intensified， and the pressure of magnetic separation-reverse flotation process is lightened， a clear improvement of technical-economical index should be promising.

Key words: Qidashan hematite ores, Coarse and fine fractions classification, Cut size, Spiral gravity separation, Magnetic separation-reverse flotation