The Energy doubler for HPM pulse compression was developed to implement miniaturized source of high power microwave. Using the Phase Shift Keying(PSK) switch, output power, which was higher than input power, could be obtained. It could output 35 MW when the input of peak power was 5.3 MW. The power gain could reach 7dB. In order to obtain the straight top waveform, some researches were done on the technology of PM–AM. These results can satisfy the requirements of miniaturized sources of high power microwave in different experiments.