Enhancing the coal adaptability of plasma ignition devices holds significant importance for assisting thermal power plants in energy conservation, emission reduction, and achieving carbon peaking and carbon neutrality goals. Currently, graded plasma combustors encounter operational challenges including combustion instability and flameout when burning low-volatility lean coal in power plants. To address these issues, this study employed numerical simulation methods. Initially, a structured mesh of the graded plasma combustor was established and its reliability was verified. Subsequently, using the controlled variable approach, the effects of three critical operating parameters - plasma power, primary air velocity, and pulverized coal concentration - on the lean coal combustion process in graded plasma combustors were systematically investigated. Finally, the operating parameters of the plasma burner were optimized to resolve ignition and combustion challenges associated with lean coal. The research results demonstrate that plasma power is the critical factor influencing lean coal ignition. To achieve stable ignition and combustion of lean coal in the plasma burner, the plasma power should not be lower than 150 kW. The primary air velocity affects the combustion temperature during the initial ignition stage, with an optimal range identified between 22-25 m/s. Furthermore, pulverized coal concentration proves to be a significant factor for successful ignition, where maintaining a relatively high concentration is essential for stable combustion - the coal concentration should not be less than 0.3 kg/kg. These findings provide important operational guidance for power plants utilizing plasma burners in lean coal ignition applications.