For the attack, interference and detection of the target, the amplitude of the UWB time-domain pulse source directly affects the intensity and effect. The Marx circuit based on avalanche transistors is widely used to generate such signal sources. The traditional Marx circuit can increase the amplitude of the output voltage to a certain extent. However, due to the low power capacity of the avalanche transistor, the output voltage of the Marx circuit of the avalanche transistor is low. The amplitude will reach saturation with the increase of the number of stages. To generate a higher amplitude pulse signal, this study comprehensively adopts the means of increasing the trigger signal and using a broadband power combiner. Finally it uses a 26-level Marx circuit as the trigger signal, by the method of 4-channel 40-level Marx circuit for power synthesis, the output voltage amplitude is 8.7 kV, the rising edge is about 180 ps, and the impact of high trigger signal on the avalanche transistor Marx circuit is analyzed through mechanism. The experiment was confirmed.