In order to explore the adaptability of the existing merging area in highway to autonomous vehicles, the influence of the acceleration lane length and the visibility triangle angle of existing highway merging area on the automatic traffic flow was analyzed, and results were compared with those of traditional traffic flow. Based on the characteristics of autonomous vehicles in terms of perception, car-following, and lane-changing behaviors, as well as the collaboration with surrounding vehicles, the Krauss car-following model and LC2013 lane-changing model were improved to adapt to the characteristics of autonomous vehicles. According to the lane-changing characteristics of the vehicles, a formula was established for calculating the acceptable safety gap when changing lanes, and the car-following model parameters were adjusted while fulfilling the requirement of lane-changing safety. Results show that under the existing plane design parameters of merging area in highway, the safety, efficiency, and stability of automatic traffic flow were better than those of traditional traffic flow. Compared with traditional vehicles, the number of collisions of automatic traffic flow reduced by nearly 100%, average delay reduced by 60% to 71%, average vehicle speed increased by nearly 20%, and the speed was more stable. Under different plane design parameters of merging area, the number of collisions of automatic traffic flow was 0, the average delay was maintained at around 0.65 s, and the average speed was stable at 33-34 m/s. The existing plane design parameters of merging area in highway well adapted to the autonomous vehicles in terms of safety, efficiency, and stability, and the parameter values of the merging area had little effect on the autonomous vehicles.