Abstract: In order to investigate the influence of insulation oil flow velocity on the collision frequency and aggregation characteristics of fiber impurity particles in converter transformers, uniform and non-uniform DC electric field environments were simulated to explore the collision frequency of particles under different oil flow velocities and radius sizes. At the same time, a high-voltage direct current platform was built to explore the agglomeration characteristics of particles under different oil flow velocities. The results showed that in a uniform DC electric field, particles with a radius of 50 μm collided up to 58 times at an oil flow velocity of 0.2 m/s. In an non-uniform DC electric field, when the oil flow velocity is 0.2 m/s, the collision frequency of particles tends to zero. In addition, when the oil flow rate is 0.02 m/s, particles are prone to aggregate on the electrode surface. When the oil flow velocity increases to 0.05 m/s, it is difficult for particles to form stable small bridge structures. The flow rate of insulating oil can affect the collision frequency and aggregation characteristics of particles, providing important reference for the optimization management of converter transformer oil.