The experimental study on the large transformer under the lightning impulse voltage is of long period and high cost. The experimental study on the reduced-scaled model has good economic performance

and it is easy to obtain valid data. The results can be compared with the simulation results. In order to design a scaled model with the electrical characteristics of the original model

the similarity formulas of the transformer under lightning impulse voltage are derived according to the similarity theory. The reduced-scaled model is designed. The electric field and magnetic field distribution of the original model and similarity model under corresponding motivation are studied by simulation.The winding voltage waveforms of the original model and similarity model under corresponding impulse voltage are calculated by multi-conductor transmission line model. The error between the original model and the scaled model is less than 5%. The distribution voltage distribution of winding is measured. The results show that the structure of the outgoing lines affects the electrical characteristics of the winding. It is necessary to further study the correction method.