Abstract: In order to study the influence of the coaxial rotating magnetic field on the separation effect of the dense me⁃ dium cyclone，the permanent magnets are placed coaxially at 80，120 and 160 mm from the interface of the cone and cone，and a three⁃phase asynchronous motor is used to control the rotation speed of the permanent magnet. And the direction，the -3mm coarse slime separation test is carried out under four conditions: no magnetic field，static magnetic field，the rotation direction of the permanent magnet is consistent with the direction of slurry feeding， and the rotation direction of the permanent magnet is opposite to the direction of slurry feeding. Select the non-mag⁃ netic field，static magnetic field at a distance of 120 mm from the barrel⁃cone interface，the rotation direction of the permanent magnet is consistent with the slurry feeding direction and the speed is 851 r / min，the permanent magnet ro⁃ tation direction is opposite to the slurry feeding direction，and the speed is 421 r / min four test points for reselection effect evaluation test，and use ANSYSMAXWELL analysis software to simulate and analyze the static magnetic field. From the results of the separation test，it can be seen that the ash content of the clean coal and tailings in the stat⁃ ic magnetic field is lower than the ash content of the clean coal and tailings in the non⁃magnetic field; the rotation di⁃ rection of the permanent magnet is consistent with the direction of the slurry feeding. The ash content of coal and tail⁃ ings is higher than the ash content of clean coal and tailings under a static magnetic field; when the rotating direction of the permanent magnet is opposite to the direction of slurry feeding， the ash content of each particle size of the cleaned coal is lower than the ash content of the cleaned coal under the static magnetic field or is basically the same ，The ash content of the tail coal is higher than the ash content of the tail coal under the static magnetic field or basically the same.From the evaluation results of the reselection effect，we can see:δp Non-magnetic >δp(+851) >δp(-421) > δp Magnetostatic; Ep Non-magnetic > Ep Magnetostatic ≈ Ep(+851) > Ep(-421) . The separation density under static magnetic field is 0.090 g / cm3 lower than the separation density under no magnetic field，but the separation accuracy is improved; the separation density when the permanent magnet rotates is between no magnetic field and static magnetic field. The ac⁃ curacy is higher than or equal to the separation accuracy when there is no magnetic field and static magnetic field. The separation density when the rotation direction is the same and the rotation speed is 851 r / min is higher than that when the rotation direction is opposite and the rotation speed is 421 r / min. The separation density，but the separation accuracy is lower than the separation accuracy when the rotation direction is opposite and the speed is 421 r / min.The simulation analysis of the permanent magnetic field reveals that the permanent magnet placed in the cone can re⁃ duce the separation density of the dense medium cyclone. The reason is that the oblique downward magnetic force at⁃ tracts more magnetite powder to the bottom orifice.，And removed from the underflow port，thereby reducing the density of the dense medium cyclone separation. When the separation direction of the permanent magnet is opposite to the feeding direction of the slurry，it will accelerate the magnetite powder inside the cyclone and help improve the separa⁃ tion accuracy.