Abstract: Beneficiation experiments of on-site mixed magnetic concentrate by using a new type of collector DMP-1 at normal temperature was conducted，in order to improve the concentrate of reverse flotation indices from Sijiaying-Yanshan plant，and solve the problems of original collector requires warming in flotation. The results showed that，iron concentrate with iron grade of 64.65% and iron recovery of 78.64% was finally achieved by dealing with the on-site mixed magnetic concentrate with iron grade of 39.05%，through the process，derived from experiments，of single-stage roughing，single-stage cleaning and three-stage scavenging，and middles back to the flow-sheet in turn. The new type of collector DMP-1 well adapted to temperature variations，and iron concentrate with iron grade of 62.13%，iron recovery of 60.60% was also achieved even at temperature 14 ℃ by single-stage roughing and single-stage cleaning open circuit reverse flotation process. X-ray diffraction(XRD) and scanning electron microscope(SEM) analysis showed that DMP-1 had good selective floating performance to quartz,dolomite and the like gangue minerals. That fine quartz particles，adsorbed and covered on relatively big iron particles，could not effectively dispersed and was depressed accompanying with iron minerals，is the main reason for relatively low grade of iron concentrate. Fine iron particles float by adsorbed and covered on relatively bigger gangue particles or in form of barren associated particles is the main reason for loss of iron.

Key words: DMP-1 collector for room temperature, Mixed concentrate of magnetic separation, Micro-fine disseminated iron ore, Quartz