Abstract: In this paper it has been reported on the low frequency preionization discharge supply,which is used for first high power CO laser in China developed by ourselves.The parameters of the supply,such as voltage output,current output and frequency,are 0～30kV,0～300mA and 1～20kHz,respectively.The preionization discharge supply has the feature of design simple,compact dimensions and has been successfully applied to the high power CO laser.