The development of anisotropic etching process for Pb,SrTiO3 PST thin films is an important task to provide a small feature size and an accurate pattern transfer. Etching characteristics of PST thin films were investigated using inductively coupled plasma etching system as functions of Cl2/Ar gas mixing ratio. The PST etch rate increased with the increase of chlorine radical and ion energy intensity. It was found that the increasing of Ar content in gas mixture lead to sufficient increasing of etch rate. The maximum etch rate of PST film is 56.2 nm/min at Cl2 / Cl2+Ar of 0.2. It was proposed that the sputter etching is a dominant etching mechanism while the contribution of chemical reaction is relatively low due to low volatility of etching products.The electron temperature and plasma density were measured by using the Langmuir probe Hiden Analytical Ltd, ESPION.The mass and the ion energy distributions IEDs were measured with a Hiden EQP plasma probe Hiden Analytical Ltd, EQP 510 that consists of an electrostatic ion energy analyzer ESA in series wi tha 高級朗繆爾探針（Langmuir Probe）