In order to improve the penetration window of PM?.? fine particulate matter in the line-plate electrostatic precipitator and improve its collection efficiency of ultrafine particulate matter, the finite element method is used to analyze and simulate the coupling process of the physical fields such as flow field, electric field, particle charge and particle motion in the double cathode electrostatic precipitator. The Poisson equation and partial differential equation are used to describe the electric field, the standard k-ε turbulence model is used to describe the flow field, the Lagdese model is used to describe the charge mode of the particles, and the Lagrangian model is used to describe the motion state of the particles. A model of a dual cathode precipitator is built on the Comsol simulation platform, and the dual cathode is studied to improve the efficiency of electrostatic precipitator. The numerical simulation results show that under the same discharge electrode voltage, with the increase of the incident velocity of the particles, the influence of the electronic wind on the overall velocity of the particles in the flow field gradually weakens, which makes the velocity difference of the particles in the flow field smaller; with the increase of the auxiliary cathode voltage, the horizontal displacement required for various particles with different inlet velocities to reach the dust collection plate gradually decreases; when the incident velocity of the particles is 0.5 m/s, the auxiliary cathode voltage can be increased to -25 kV compared with the non-auxiliary plate, which can make the dust collection efficiency of 0.1 ~ 1.0 μm fine particulate matter can reach 98.5%; when the incident velocity of particles is 0.5 m/s, the discharge electrode voltage increases from -20 kV to -25 kV under the same auxiliary cathode voltage, which can increase the dust collection efficiency of 0.1 ~ 1.0 μm fine particulate matter by 25%.