3D terrain is an important part of flight simulation system. Airport runway is an indispensable part of the flight landing process, and its authenticity directly affects the authenticity of flight simulation system. In order to create 3D terrain with high realistic airport runway, the terrain data in FlightGear, airport texture data and Google Maps texture data are used under Unity. Through the method of dynamic creating terrain grid and material, combined with multithreading technology, the parallel creation of 3D terrain is realized. The experimental results show that the proposed method can quickly create 3D terrain including high realistic airport runway, and can be used to simulate 3D terrain in flight simulation system.