To reveal the distribution characteristics of the arc-plasma and the behavior of the flow field and further analyze the relationship between external parameters and arc behavior, this study conducts a numerical simulation of a coaxial dual-chamber plasma generator based on Magneto Hydro Dynamics (MHD) theory. The research investigates the correlations among arc voltage, cathode spot distribution, and airflow parameters with the axisymmetric model by incorporating coupled calculations of the flow field and electromagnetic field. The simulation results indicate that arc voltage is relatively insensitive to radial airflow; within the studied parameter range, fluctuations in radial airflow pressure have a maximum impact of only 4.2% on arc voltage. In contrast, arc voltage exhibits a strong positive correlation with axial airflow velocity, and a fitted correlation equation has been obtained. Temperature and velocity distribution analyses show that the maximum nozzle temperature exceeds 3 500 K, ensuring sufficient ignition capability for low-quality coal and stable combustion performance. Moreover, the results confirm that, under proper airflow configuration, the coaxial dual-chamber structure enables plasma igniters to achieve both high power and extended electrode lifespan. It reveals the anti-ablation mechanism of this structure, namely, the alternating sweeping effect of the two gas flows—the axial flow primarily controls the output power, while the radial flow regulates the arc root position through periodic fluctuations, thereby preventing single-point erosion and extending the electrode lifespan. Furthermore, the study further identifies the balance point between the two gas flows through optimized design experiments, providing theoretical support for future research on the long-term durability of plasma generators.