When airborne missile launched from UAV, its exhaust jet has an impact on UAV airfoil and safety. This study is based on two-dimensional unstructured dynamic grids and standard k-omega tow-equation turbulence model of the software Fluent. In this research difference between missile ignition firing and ignition firing after ejection was analyzed, and these two results were compared. The results show that the rail-catapult integrated launcher can reduce aerodynamic influence on airfoil caused by missile exhaust jet stream. The results will provide certain reference for research of rail-catapult integrated missile launcher of UAV.