The influences of switch prefire in different LTD cavities on the other cavities with shorted or open load have been researched based on the 50 stages linear transformer driver module. It is shown that the induced voltage in the other cavities is very low, and the amplitude of voltage signal will decrease with increase of distance. The maximal induced voltage is 2.43 kV when switch prefire occurred in neighbouring cavity at voltage of ±83 kV. The results will contribute to reliability model constructing, analysis and assessment of large scale LTD generator.