To safely, efficiently change lanes among human drivers, autonomous vehicles (AV) should act as close as possible to human to decide when to friendly cut in and seamlessly cooperate with surrounding vehicles. However, it is still not fully clear about how AV cut-in behavior would influence on human drivers. This paper comprehensively analyzes the influence of AV cut-behavior on human drivers in terms of comfort levels over different cut-in scenarios in a driving simulator. The experiment results demonstrate that the relative distance has great influence on the comfort level of human drivers compared to relative speed; and the integrated influence of relative distance and speed between AV and the behind target vehicle have an important role in the influence. These findings could provide an empirical basis for the decision-making design of autonomous vehicles.