The effects of Cl-2 inductively coupled plasma (ICP) treatment on the time dependence of work function( WF) and surface properties of indium tin oxide (ITO) were investigated. Kelvin probe (KP) measurements show that the WF after Cl-2 ICP treatment is close to 5.9 eV. The WF decrease curve of Cl-2 plasma treated ITO is fitted with double exponential functions with an adjusted R-square of 0.99. The mechanism under the decrease process is discussed by X-ray photoelectron spectroscopy (XPS). The ITO WF decrease after Cl-2 ICP treatment performs much better than that after O-2 ICP treatment and the chlorinated ITO keeps a WF increment of 0.3 eV compared with that without plasma treatment after 100 days. Other properties of chlorinated ITO surface such as morphology and transmittance change slightly. The results are significant for the understanding of degradation of Cl-2 plasma treated ITO and the fabrication of organic semiconductor devices. (C) 2014 Elsevier B.V. All rights reserved.