The system adopts online double transform structure design, completely eliminate the disturbs on the electricity net; AC/DC input with harmonic wave suppresser, stopping the harmonic wave polluting the electricity net, DC/AC convertor adopts SPWM pulse width adjustment technique, IGBT power module, and output isolation transformer. Then the ups will output pure sine wave power supply which has stable frequency and voltage ,no noise and disturb. This series of UPS can satisfy many application environment because of the high load ability, good compatibility, large range of city input voltage and frequency, output no switch time and excellent generator with matching compatibility. Perfect protective circuit, which improve the stability and reliability.