The Head-Up Display(HUD) with a image source of CRT generally has high requirements to the performanceefficiencyvolume and weight of the High-Voltage Power Supply (HVPS).Having the advantages of small sizelight weight and high efficiency etcthe PWM type HVPS has found a wide application.The principle and unit circuit of the HVPS was introduced.The contravariant mode was used in the circuit.The 27 VDC was changed into the needed high voltage through processing of power conversionvoltage boosting and transformationand dual voltage rectifying.Stabilizing of the voltage was realized by using the pulse width modulator SG1525A.