Abstract: The application of pre-concentration technology on beneficiation of lean iron ore was described.Sufficient conditions of pre-concentration for lean iron ore were provided by the effective reduction of the feeding size as the result of the application of new types crushing and grinding machines of which high efficiency cone crusher，AG/SAG and high-pressure grinding roller were the chief representative.Pre-concentration for products of 350~400 mm from coarse crushing and -3 mm from ultra-finely crushing of lean magnetite could be realized by magnetic separation.And dry or wet process of pre-concentration could be determined according to the different processes.High-intensity permanent magnetic separator provides a new way for pre-concentration of lean hematite after middle crushing.Vertical ring pulsating high gradient magnetic separator has a better effect on the pre-concentration for -3 mm lean hematite.The development tendencies in pre-concentration of lean iron ore are investigation of efficient crushing equipment and process，research on adaptability of magnetic separator to the characteristics of lean iron ore and production environment，further research and application of permanent high-intensity magnetic pre-concentration for lean hematite.

Key words: Magnetic pre-concentration, Size of pre-concentration, Lean magnetite ore, Lean hematite ore