Abstract: In this paper, the one-dimensional fluid model is used to study the discharge characteristics of Ar/O₂ plasma at low frequency (100 kHz). The effects of pressure and frequency on plasma density, ionization rate, electron temperature and ion energy bombarded to the upper plate are discussed. The results show that the γ mode dominates in the low-frequency Ar/O₂ discharges, while the drift-ambipolar (DA) mode is relatively weak, but exhibits significant drift electric field and ambipolar field. Electrons are mainly concentrated at the upper electrode, and ion energy bombarded to the upper plate is much higher. With the increase of discharge frequency, the mode initially undergoes a transition, whereby it is first shifted from the γ / DA hybrid mode, which is predominantly governed by the γ mode, to the α / DA hybrid mode, which is predominantly governed by the DA mode, and then transitions into the α / DA hybrid mode dominated by the α mode. The mode transition has a significant effect on electron density, electron temperature and ion energy bombarded to the upper plate. When the pressure increases, the mode conversion phenomenon will also occur. However, the plasma density in the low frequency region and the high frequency region shows a completely different trend with the pressure. More importantly, as the pressure increases, the DA mode in the high frequency region is obviously enhanced, and the DA mode in the low frequency region is weakened.