Abstract: The output power of the RF power supply is one of the key parameters affecting the spheroidization of powders in RF plasma. Based on the power difference method, the effective power transmitted from the DC side of the RF power supply to the plasma was determined by comparing the power output characteristics under no-load and plasma-load conditions. RF plasma was then employed to spheroidize micron-sized ZrO? powders, and the effects of different effective input powers on particle morphology and size were analyzed. The results show that the RF transmission efficiency is determined by the resonant circuit of the RF power supply and remains approximately constant within the operating range of the electron tube. As the effective output power at the coil end increased from 42 kW to 49 kW, the powders gradually transformed from partially molten to fully molten, local vaporization was significantly enhanced, and the powders exhibited markedly improved sphericity and density, along with reduced particle size and narrower size distribution. The phase structure of the powders after RF plasma treatment remained largely unchanged. These findings provide a power reference and guidance for subsequent simulations, experimental studies, and process optimization of RF plasma powder spheroidization