To realize the miniaturization and lightweight design of Tesla transformer with high output voltage, the relationship between the surface flashover characteristics of support insulators and the surface electric field in a 0.5 MPa SF₆ gas environment is studied. The electric field simulation model of Tesla transformer is established using the finite element method. Combined with experimental research, the surface flashover process of support insulators is analyzed, and the field equivalent experimental methods and conclusions of key insulation components of Tesla transformer are clarified. Based on the above analysis, the structure of support insulators is optimized. After optimization, the maximum electric field along the concave side of the support insulator decreases by about 81.5%, the average value of tangential electric field intensity decreases by about 10.3%, while the average value of normal electric field intensity decreases by about 30%, the distance along the surface increases by 11.8%, and the electric field unevenness coefficient decreases from 5.03 to 1.2. The electric field distribution is significantly improved, and the optimized insulator can withstand 1 MV negative polarity microsecond pulse voltage.