With the continuous progress of modern high-speed railroad technology, the speed of train operation is increasing, and its aerodynamic effect when traversing the tunnel is also getting more and more attention from researchers. In this paper, we constructed a three-dimensional flow field model of the wrist-arm insulator in the tunnel and considered the train speed, tunnel structure, size and position of the wrist-arm insulator, and other factors, and then through the simulation software, we simulated the change of the airflow in the tunnel when the high-speed train enters the tunnel. Through the simulation analysis, we obtained the characteristics of the flow field distribution around the wrist-arm insulator in the tunnel when the high-speed train crosses the tunnel. The results show that when the train crosses the tunnel at a high speed, the airflow inside the tunnel is strongly squeezed and disturbed by the train, forming a complex airflow field. When the train passes by, the wrist insulator will be impacted and squeezed by the high-speed airflow generated from the train, resulting in significant changes in the airflow velocity and pressure distributions on its surface. These changes not only affect the electrical performance of the arm insulator but also have a direct impact on its structural stability and service life.