In the context of energy transition and sustainable development, multi-energy complementary technology has become an important means to optimize energy allocation. As the proportion of new energy connected to the grid increases, it brings many challenges to the stability of the power system. China's uneven energy distribution, the rapid development of ultra-high voltage direct current (UHV DC) transmission, the resulting power system transient voltage stability problems are also increasingly prominent. In this paper, we take the multi-energy complementary system sent out by UHVDC as the research object, and construct a model with the help of power system simulation software to discuss the impact of three-phase short circuit faults on the converter bus voltage under different conditions. The impact of three-phase short-circuit faults on the UHVDC transmission system is evaluated by analyzing the transient voltage stability margin through the multi-binary table.