Abnormal streamer discharge phenomena in ultra-high voltage power transmission equipment are strongly influenced by the spatial distribution of airborne particles. This study develops a coupled fluid model comprising a streamer discharge fluid module and a particle charging module, to investigate the influence of particle size and density on discharge branching, electron density distribution, electric field evolution, and related physical processes. The streamer discharge fluid module supplies electron and ion density data to the particle charging module, while the particle charging module, in turn, delivers the charged particle continuity source term and the charge source term to the streamer discharge module. The study reveals that polarization of large-size particles enhances electric field intensity adjacent to the outer particle surface, promoting surface streamer initiation and suppressing the propagation of the volume streamers. The smaller the interparticle distance, the less likely a new volume streamer is to be observed. For the circumstance of smaller-size particle, the quantity of streamer branches exhibits a substantial increase attributable to the electric field source term and the continuity source term arising from the particle charging process via the electron and ion adsorbing. As a result, the electron density within the streamer drops significantly by approximately 61% in the presence of the particle distribution. Concurrently, the evolution of the electric field amplitude across the discharge gap undergoes a distinct reversal, driven by the particle charging inside the particle distributing region. In both larger-size and smaller-size particle scenarios, the accumulated surface charge distorts the local electric field, thereby suppressing upward streamer propagation through the particle distributing region while simultaneously enhancing the streamer’s velocity as it exits this region and advances toward the bottom electrode.