Abstract The microscopic dynamics and formation mechanism of Trichel pulse discharge are investigated. A nonequal current transient effect exists in the Trichel pulse discharge. By reducing the limiting current resistance, the simulated current waveforms of Trichel pulse discharge are qualitatively and quantitatively consistent with those in the experiment. The dominant positive ions vary at different stages, which originate from the evolution of dominant reactions for the generation and consumption of charged particles. The existence of positive and negative charged layers results in the attenuation of the electric field at the rising edge of the Trichel pulse. The formation of the Trichel pulse originates from the changes in spatial charge density, resulting in alterations in the spatial electric field and ionization rate.