For research on the aerodynamic characteristics of structures undergoing the acting of the sudden-change flow, the wind tunnel experiment for simulating the sudden-change airflow was introduced in this paper. Firstly, a profile of downburst gust was simulated using an active control wind tunnel. Secondly, the approach of change-step change airflow was utilized to simulate the time history of sudden-change airflow. Finally, a high-rise structural model was placed into the sudden-change airflow in order to observe the variation characteristics of wind pressure on the structural surface and of the structural aerodynamic parameters. Experimental results showed that the analytical profiles of downburst gust fitted over 90 percents to the experiment results simulated in this active control wind tunnel, and the sudden-change airflow generated a high unsteady lift on the whole high-rise structures and a big unsteady wind pressure on the surface of structures.