A new characterization model for rotating blade-casing rub-impact is deduced based on the law of conservation of mechanical energy. This model includes not only the bending deflection of blade during rub-impact, but also the casing deformation due to impact with introducing the equivalent stiffness into characterization model. The model is used in rub-impact between the taper blade and the casing in addition to straight blade. Besides the operating conditions, such as, rotating speed, friction coefficient and so on, are also considered and the relation between the rub-impact force and each parameters is discussed. The model is verified by the rub-impact force data obtained through blade-casing rub-impact experimental test. It is shown that the model and test data are approximately identical, and the rub-impact force is described preferably by the new model through the comparison with existing models.