Magnetic dipole model is a kind of important method for studying magnetic leakage of ferromagnetic components with defects. In this paper, an elliptic cylinder magnetic dipole model is represented. Some magnetic leakage features of typical defects, such as crack, hole, pit and slot, which are normal to surface of components are studied by the using model. In addition, the coordinate conversion method is combined with the model to study magnetic leakage features in case that defects slope an angle to the component surface. Theoretical results are in good agreement with experimental ones. It provides a method and model to process magnetic leakage signal in order to identify and evaluate defects for ferromagnetic components.