Abstract: A high-voltage soft coaxial feeder is developed in order to meet the research needs of high-power microwave power technology, as well as high power pulse technology. According to the actual application of the feeder, and under the conditions of low voltage, high voltage, time and frequency domains, we test the pulse power attenuation and transmission characteristics of the high-voltage feeder respectively at different voltages and air pressures. The test results are analyzed and compared with each other, which show that the pulse signal power attenuation is 0.03 dB/m, meeting the technical requirement of 0.05 dB/m.