The tunnel section of the road is a frequent occurrence of traffic accidents. The occurrence of these accidents is related to the impact of the driving environment of the tunnel section on the driver's vision. The driver relies mainly on the vision system to obtain different road information. This paper uses the ASL mobile eye monocular eye tracker to record the driver's eye movement parameters at the tunnel entrance section to analyze changes in the driver's visual search mode, namely the driver's gaze behavior and saccade behavior. In this paper, it is concluded that as the driver enters the tunnel, the gaze distance decreases, especially at the entrance to the tunnel. In the entrance section of the tunnel, the driver's gaze area is mainly distributed in the far ahead area and the far-right area in the front. The gaze time accounts for 28.72% and 59.24% of the total gaze time respectively; the number of gaze accounts for 35.18% and 50.75% of the total gaze times respectively. During the driving process of the tunnel entrance, the driver's gaze duration is the highest in the period of 0 similar to 50 ms. At the same time, the proportion of gaze duration is increased in the period of 50 similar to 100 ms, 100 similar to 150 ms, and 150 similar to 200 ms. The visually sensitive phenomenon of the driver mainly occurs within the 20 m section of the tunnel entrance and exit.