Abstract: At present, the steel industry has become the focus of air pollution prevention and control. To solve the difficulty in collecting PM_2.5 fine particles and achieving ultra-low emission of dust, based on the method of computational fluid dynamics-discrete phase model (CFD-DPM), the influence of different magnetic field forms, such as magnetic field generated by magnetic fiber and high-gradient magnetic field, on the performance of PM_2.5 collection in the iron and steel industry was studied. Through X-ray diffraction (XRD) analysis, it was found out that the dust produced in the iron and steel industry production process has magnetic characteristics due to the presence of Fe₃O₄ and elemental Fe, furthermore, the method of using magnetic field to enhance the PM_2.5 collection performance of single fiber was proposed. The results show that the magnetic field generated by the magnetic fiber will form a gravitational region around the fiber, and the high-gradient magnetic field will form two gravitational regions and two repulsive regions around the fiber. In terms of the collection ability, when particle diameter d_p between 0.5 and 1.0 μm, inlet velocity v≤0.2 m·s⁻¹, the collection ability of magnetic fiber under the high-gradient magnetic field is stronger than that of the single magnetic fiber. If magnetic field intensity H=0.5 T, magnetic induction intensity B=0.01 T, and v=0.1 m·s⁻¹, the high-gradient magnetic field can improve the single fiber collection efficiency by 28.32 times as much as the original; if B=0.01 T, v=0.1 ms⁻¹, the magnetic field generated by the magnetic fiber can improve the single fiber collection efficiency by 4.037 times as much as the original. In terms of the collection law, in the magnetic field generated by the magnetic fiber, when the magnetic flux density B≥0.03 T, the collection efficiency of magnetic single fiber on PM_2.5 decreases with the increase of inlet velocity speed and then tends to be stable. When B<0.03 T, the collection efficiency decreases with the inlet velocity speed. The collection efficiency increases with the increase of dust particle size. For the high-gradient magnetic field, the single fiber collection efficiency of PM_2.5 particles also decreases with the increase of inlet velocity speed. When v>0.4 ms⁻¹, the collection efficiency is 0. The larger B is, the faster the collection efficiency decreases. The collection efficiency increases first and then decreases with a increase in dust particle size.