A magnetic separator is a magnetic sorting machine based on material magnetism difference, which applied to iron elimination of powder grain, wet magnetic separation of magnetite, pyrrhotite, roasting ore, limonite and other materials of coexistence below 3 mm and remove iron for coal, non – metal ore, building materials and other materials. It is one of the most widely used high commonality and machines. It is composed of base, upper magnetic system, lower magnetic system, cage, hollow shaft, and concentrates tank and transmission devices. Base installation should make hollow bearing bush as a benchmark to measure the elevation and levelness. Positioning lower magnetic system should base on the docking station. The gap adjustment between cage and upper and lower magnetic system must be accurate whose limited deviation is 0 + 1 mm. In 2005, the concentrator factories adopt high frequency Vibrating Screen and composite dam selection technology and flashing magnetic separator. As a result, the ore dam final grade was reduced by an average of 2.44%. Figures showed that we annually may elect from the dam 31,190,000 tons of iron ore concentrate, with the concentrate grade 67. 13%, this can achieve annual benefit of RMB 54 million. Production practice of iron ore dam re-election indicates that ore concentrator factories discharge 2.28 million tons of dam a year. The dam processed by the JHC rectangle ring type magnetic separator, and we gained elected rough ore concentrate, and then the concentrator is pumped to a separate built-in concentrate plant. It will go through weak magnetic separation, grinding-classification, magnetic dewatering tank and double drums weak magnetic separation process, and finally we get the final ore concentrate. Many users do not understand why the concentrator needs to deal with the dam. They think that is a way with low efficiency. If they have time, it s better to dressing by magnetic separation directamente para the source ore, which will increase the working efficiency.