Abstract: In this paper, the one-dimensional fluid model is used to study the characteristics of Ar /O₂ discharge with a driving frequency of 40 kHz. The effects of external conditions such as voltage, pressure and plate spacing on the ionization rate, plasma density, electron temperature, and ion energy at the plate are discussed. The results show that the γ mode is dominant in the low-frequency discharge, the DA (drift-ambipolar) mode is very weak and almost negligible, and there is no mode conversion phenomenon when the external parameters change. Another characteristic of low-frequency discharge is high ion energy. In addition, the increase in voltage makes the plasma density and O₂⁺ energy increase rapidly, and the electron temperature in the sheath region increases with the increase of voltage, but the electron temperature in the plasma region decreases with the increase of voltage. The increase in pressure and plate spacing will also increase the plasma density and ion energy, while the electron temperature in the sheath region and the plasma region decreases with the increase of pressure and plate spacing.