For high voltage 10kV power supply system, detailing the cascaded static synchronous compensator (STATCOM) structure of the device. Cascaded H-bridge inverter module as the primary topology is used to the device .The device has the advantages of a small inverter output voltage harmonics and high grade. This paper designs cascaded H-bridge inverter unit parameters. This article uses unipolar modulation of CPS-SPWM by double frequency technology to control the pulse switch device and implements control of cascaded multilevel STATCOM. We build a prototype of STATCOM. Experiment proves the effectiveness, validity and superiority.of the scheme described in this article by experimental prototype.