To reveal the changing process of drivers’ pupil size during driving were carried out into of tunnels, experiments eight drivers drived into four tunnels at different time. And their pupil size were recorded with eye tracker in the driving process. The recorded raw data by eye tracker was analyzed, wavelet transforms method was taken to process the data, and the pupil size changing curves of drivers when they drive into tunnels. From the curves analysis, it has been found that the individual difference exist on different drivers’ pupil size; There was a degree of randomness of pupil sizes amone repeated test of the same driver; the drivers’ pupil enlarged gradually when they driving into tunnels, and enlarged violently nearby tunnel’s threshold; the pupil size changing tendency of different driver exists some difference; drivers’ pupil size was influence not only by adaptation luminance, but also by their psychological factors.