A total of 32 subjects are recruited to conduct real vehicle tests in two adjacent tunnels of the Guizhou section of the XiamenChengdu expressway to explore the influence of shading shed at the connection section between two tunnels and the length difference of the upstream tunnel on drivers′ visual adaptability and load characteristics. Then, the data of pupil variation characteristics are collected and exported by the eye tracker. Further, the eye movement rule of drivers is analyzed by the pupil area change and average change rate. Finally, the maximum transient velocity of pupil area(MTPA) is used as an index to evaluate the driver′s visual load degree in the connection section of two tunnels, and the oneway analysis of variance is used to test the difference of MTPA. Research results reveal the following: (1) When the connection section is equipped with a shading shed, the drivers′ pupil area changes more smoothly, and the varying rate of the pupil area is also significantly reduced, mainly in the －2.0~2.0 mm2·s－１ range.  Moreover, the drivers′ MTPA is reduced by an average of 25.1%. (2) When the connection section is equipped with a shading shed and the upstream tunnel is a long tunnel, the pupil area of drivers in the exit zone will decrease by 50 m in advance. Furthermore, the MTPA of the drivers at the exit zone of the upstream tunnel is significantly higher than that of the upstream tunnel when it is a short tunnel, with a 30.1% increase in visual load but a 27.1% decrease in visual load in the downstream tunnel entrance zone. It is concluded that the shading shed at the connection section between two tunnels can improve drivers′ adaptability to changes in light environment and effectively reduce drivers′ visual load. In addition, the length difference of the upstream tunnels will affect drivers′ adaptability to the change in the light environment.