High voltage DC power supply is widely used in research and application areas of electron beam. Recently the method of decreasing ripple is a research hotspot due to the ripple of high voltage is the very key factor to quality of beams. This paper studies a novel circuit topology, which is comprised of a high bridge converter and a double polarity Cockcroft-Walton circuit with unsymmetrical capacitors. The experimental results show that the ripple is lower than 0.06% when the output voltage and current are 100 kV and 25 mA, respectively. Meanwhile the storage energy of high voltage units is only 0.85 of traditional circuit.