With one unmanned civil plane as investigated object, the lift, drag and pitching-moment coefficients are calculated by AVL, an eddy-lattice-method based aero-dynamics software. In order to ensure the rationality of the unmanned plane on aero-dynamics properties, the calculated results are further discussed on theory. It is shown by flight-test that the present unmanned plane is successful on design, and is excellent in lift/draft properties and longitudinal-stability as well.