A useful method is proposed to analyze a short interfacial crack emanating from the corner of a rectangular inclusion. We first analyze the singular stress field (and the corresponding singularity intensity factor H) without the crack in an infinite medium having the rectangular inclusion. The singular stress field (and the corresponding stress intensity factor K) at the tip of the short interfacial crack lying in the interface of the rectangular inclusion is also analyzed, giving the relation between H and K. With this relation, the stress intensity factor K is easily obtained for the case of a short interfacial crack from the corner of a different rectangular inclusion with different external boundary. This method is based on the assumption that the singular K-field is embedded in another singular H-field, which is much smaller than the specimen geometry. To meet the assumption, it is found here that the eigenfunction corresponding to the next smallest eigenvalue of the singular H-field has to be considered. An example is presented to show the usefulness of the present method, where a short interfacial crack from the corner of a rectangular lead frame in epoxy compound used in electronic packaging is analyzed. It is found that the result of the present method is in good agreement with that of the well-known method.