To meet the ultra-high temperature heating requirements for ground thermal strength tests of hypersonic flight vehicle leading-edge structures. This paper proposes a design method for high-power graphite heating elements. The performance of these elements is evaluated through theoretical analysis and experimental validation. First, based on the electrothermal coupling principle, a multiphysical field coupling analysis model is established. This model calculates stress distribution, temperature distribution, and deformation under different voltages, enabling prediction of maximum heating power. Second, a systematic study is conducted on the effects of geometric parameters on heating element performance. The study reveals patterns of radiative heat flux density and heat flux uniformity as geometric dimensions change. These findings lead to the formulation of a design scheme for high-power graphite heating elements. Finally, experimental validation demonstrates that the optimized design achieves a maximum radiative heat flux density of 1.593 MW/m2 and a maximum heating power of 148.5 kW. These results satisfy the ultra-high temperature heating demands for hypersonic flight vehicle ground testing. They also provide reliable technical support for evaluating thermal protection system performance.