Abstract: The leakage inductance of round litz-wire high-frequency transformer (HFT) affects the performance and operation life of power electronic devices, therefore precise calculation and control of leakage inductance are required. However, the body structure of HFT is three-dimensional, and the accuracy of traditional calculation models based on one-dimensional assumptions cannot be ensured. Therefore, based on the principle of image method, this paper simplifies the leakage magnetic field distribution of HFT using double two-dimensional equivalent method. Considering the influence of high-frequency eddy current effects on the leakage magnetic energy inside the round litz-wire, we establish the double two-dimensional leakage inductance analytical calculation model for HFT. The leakage inductance variation characteristics of HFT under the conditions of opening air gap of magnetic core and winding interleaving are analyzed using the proposed model. The double two-dimensional leakage inductance analytical calculation model is applied to the optimization design process of HFT, and two HFT prototypes with transformation ratios of 200 V/200 V and 300 V/600 V are designed and manufactured. The leakage inductance of the prototype is measured through experiments, and the global average deviation between model calculation values and experimental measurement values is less than 2%, which verifies the accuracy of the proposed model. Finally, by comparing and analyzing the applicability of the model in this paper, it is concluded that the computational accuracy and time cost of the model will increase with the increase of the image layers and grid divisions. This study provides a reference for the application of the proposed model in round litz-wire HFT optimization design.