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Truck technology depends decisively on the track structure of the material after irradiation. In order to reveal microstructures of the ion-tracks, many techniques have been applied to characterize the track. Conductometrie method is wildly used in the area as it can monitor in-situ the pore formation and growth processes that are closely related to structures of the ion track[1].In this study, polyethylterephthalate films (PET, 38 μm thick) were irradiated with Xe ions of 450 MeV, 3 × 105ions/cm2. Before etching with aqueous 0.3 M NaOH solution at 40℃, the samples were illuminated with UV light (λ＞310nm) in air for different time durations. Pore growth processes during the etching were monitored by the conductometric measurement. Fig. 1 shows the measurement results of radial etching rate of the pore growth in dGl/2/dt (Ω-1/2s-1) with the etching time.a. Without UV illumination, b. UV illuminated for 60 min, c. UV illuminated for 180 min, d. UV illuminated for 720 min As shown in Fig. 1, the etching processes changed dramatically with UV illumination time. (1) The break through time reduced with increased sensitization time, from 8× 104S of the control to about 1 × 104s of the 720 minutes UV illumination. (2) With increased UV illumination time, the shape of the pore growth rate curve changed greatly, f-mally became a shape with a peak and a vale. Formation of the peak implies that pores tended to break-through on completing the UV-light illumination, whereas the vale can be related to the slower etching rate in the track halo where most molecules had been crosslinked by the heavy ion irradiation. After etching for sufficient long time, the pore grew at a constant rate determined by the bulk etching rate.To interpret the measurements, numerical analysis and fitting were carried out, from which information related to the track structures and variations with the UV illumination was obtained.