It is identified by the modulated optical absorption spectra and ESR spectra that the main form of the oxygen components in KC1:OH- is O2-. The density of O2- in the sample increases with the increasing of the irradiation time until the(OH)- ions are completely destroyed by irradiation. O2- is a very stable radical,but no direct effects on the stability of F2+ centers are detected. The energy configuration of O2- is also discussed according to the ESR data.