The inverted T-shaped arrangement of insulator strings can improve the AC and DC flashover voltage of insulator strings in polluted and icing environments, but its flashover characteristics under lightning impulse voltage lack research. In order to investigate whether the inverted T-shaped arrangement effects the lightning withstand level of insulator strings, this study used LXY-70 glass insulators as samples to explore the lightning impulse pollution flashover characteristics of the inverted T-shaped insulator strings under different arrangements and salt densities. The electric field distribution was also simulated. The results show that the lightning impulse flashover voltage of the inverted T-shaped insulator strings is inversely proportional to the salt density. The electric field strength in the horizontal tension segment is lower, with less distortion, which is not conducive to the development of local electric arcs. The flashover voltage under positive polarity and negative polarity lightning strikes is increased compared to the suspended arrangement. The percentage increase in flashover voltage with a certain creepage distance increases with the increase in horizontal string length, but the magnitude of increase is small. The inverted T-shaped arrangement can slightly enhance the lightning withstand level of insulators. These findings can provide some reference for the practical application of the inverted T-shaped arrangement in transmission lines.