Abstract:The fluid structure interaction (FSI) effect was considered in the wind tunnel test and numerical simulation for the improved Ahmed body. The validity of numerical simulation method about FSI was confirmed with body displacement data which was measured by the scaled wind tunnel test. By experimental and numerical methods, the change regulation of aerodynamic force and moment was described when FSI was considered and the internal mechanism of the change of aerodynamic force and moment was revealed. It was concluded that the FSI effect should be considered in vehicle design.