Abstract: Avalanche transistors have been widely used in nanosecond pulse generators because of their short rise time, high-frequency and other characteristics. In order to increase the output voltage amplitude, Marx circuits based on cascaded switches are often used. In this paper, diodes were used to replace some current-limiting resistors in traditional Marx circuits based on cascaded switches to reduce the energy loss, to speed up the charging speed, and to increase the repetitive frequency. The influences of capacitance and the current limiting resistor on the output voltage amplitude and frequency are analyzed. By testing the breakdown of a single BJT, the minimum on-resistance of the single BJT was calculated to be about 2.5 Ω, and the equivalent internal resistance of the Marx circuit based on cascaded switches reduced the output voltage amplitude over the load, hence multiple Marx circuits in parallel were used to increase the output voltage amplitude. By changing the number of Marx parallel modules, the influence of the equivalent internal resistance of the circuit on the output pulse was studied. By changing the load resistance, it is verified that the Marx circuit in parallel had a better boosting effect over low-resistance loads. The experiments show that, nanosecond pluses with rise time of 3.4 ns, amplitude of 2.5 kV and repetitive frequency of 15 kHz were obtained over a 50 Ω load with four Marx circuits in parallel.