In order to improve the seismic performance of the supported flexible DC converter valve, some equipment suppliers have added diagonal rod insulators between the support insulators. It is necessary to study the impact of the layout scheme and pre-tension force of the diagonal rod insulators on the overall seismic performance of the converter valve. Combined with a converter valve, finite element numerical simulation technology is used in a certain engineering project. Firstly, modal analysis is carried out to study the arrangement scheme of diagonal rod insulators and the influence of pre-tension force value on the dynamic characteristics of the valve tower. Then, the vibration mode decomposition response spectrum method and nonlinear time history analysis method are respectively used to conduct dynamic analysis of the valve tower. The results show that the addition of diagonal rod insulators can significantly increase the fundamental frequency of the converter valve tower, but the magnitude of the pre-tension force of the diagonal rod insulator has a relatively small impact on the overall frequency of the valve tower structure. The results obtained by the time history method are generally greater than those obtained by the response spectrum method. Because it can accurately simulate the nonlinear characteristic of the diagonal rod insulator which can be pulled but not compressed, it is recommended to use the time history method to study the seismic performance of pillar type electrical equipment with diagonal rod insulators.