A stabilized high voltage power supply for an electrostatic analyzer is described in this paper. The design principle has been analyzed in some detail. The output voltage of this instrument may be varied continuously from ± 5 kv to ±20 kv. Within this range the voltage stability is better than ±0.015% for about 3 hours. The ripple voltage is one part in 16,000. This instrument had since served normally for more than two years and was shown to be sufficiently simple and reliable both in operation and maintenance.