Abstract: A spiral parallel-plates Blumlein line with polypropylene dielectric and film aluminum electrodes was designed. With the gap switches connected, its discharging characteristics were studied. Simulation and experimental results show that the increase in switch inductance slows down the rising of pulses and introduces reflections. The energy loss caused by film electrode resistance lowers the pulse top. The existence of distributed capacitance coupling leads to pre-pulsing in output waveform voltage while the voltage-sharing electrodes have no effects on discharging characteristics.