Under the influence of excitation current, the primary and secondary ampere-turns of the transformer based on the CLLC resonant converter are not balanced, and the magnetic field distribution in the winding window is not uniform, so the traditional calculation method for approximate ampere-turns balance transformer is unsuitable. In this paper, the distributed air gap is used to optimize the winding loss, and a winding loss evaluation method is proposed for the CLLC transformer in the case of amp-turns imbalance. The method has a fast calculation speed and small error and is suitable for calculating the winding loss of Litz wire and other shapes. Finally, the comparative analysis of finite element simulation verifies the effectiveness and accuracy of the method.