To analyze the effect of UV-induced generation of ions in a rubbed ITO-aligned TN cell, we have measured and analyzed the VHR (voltage holding ratio) data obtained from the TN cell with and without UV-illumination. Using the theoretical model for the ion generations from HIR (high-ionization-rate) and LIR (low-ionization-rate) impurities within the LC mixture to fit the measured VHR data, we can derive initial ion concentration and ion mobility for HIR and LIR ions within the TN cell. By analyzing the VHR data measured at three different temperatures, we have obtained the corresponding ion concentrations and activation energies of ion-dissociation and ionic mobility of the LC mixture within the TN cell with and without UV illumination. The results of our investigation have showed that most of ions existed in the rubbed ITO-aligned TN cell without UV illumination were from LIR impurities. However, after UV illumination, plentiful HIR ions have been generated in the TN cell, and the physical properties of the LIR ions existed before UV-illumination have been altered slightly by the UV-illumination.