Hot-spot temperature of winding is an important indicator for on-line monitoring of distribution transformers. However, the existing on-line calculation methods for winding temperature rise do not consider the influence of foil winding structure. The structure of foil winding is identified by equivalent resistance ratio of distribution transformer under different harmonics, and comparing the heating difference between the wire winding structure and the foil winding structure, an algorithm for calculating the winding temperature rise through changes in winding resistance was online corrected. This method provides a new idea for predicting the hot-spot temperature of foil winding through the ratio of harmonic resistance.