Abstract: Tornado has significant potential of severe damage to structures and has been one of the important research topics in wind resistance&disaster prevention engineering. With the changing of global environment in recent years, large cities are attacked by tornados occasionally. The studies on tornado's effects on high-rise buildings receive concerns gradually. Presently, few investigations focus on dynamic behavior of moving tornado and the impacting wind loads on high rise buildings. The wind model of moving tornado is established and the unsteady process of a moving tornado impacting against high rise buildings is numerically simulated, then the wind flow characteristics, as well as the dynamic wind loads of tornado striking against large civil structures, are analyzed. The results show that 1) The numerical tornado models and methods adopted herein are reliable to simulate the tornado flow field, and the simulation results are in good agreement with those of experiments; 2) The wind loads of tornado striking on high-rise buildings is observed to be related with the size of target buildings. For small size case, the loads are characterized by dual peak profiles, and impacting effects and unsteadiness are relatively small, while for large size case, the loads are characterized by multi-peak profiles with strong unsteadiness and large impacting effects. 3) In the process of tornado striking on large size high-rise buildings, the main vortex is observed to be broken into several vortices, and then a complicated interaction and coupling among vortices, as well as a wake flow of building, is observed. No similar mechanical phenomenon has been reported in existing literatures of tornado investigation.