A rectifier converter of the UPS includes a rectifier discharge reuse module, a first mains switching module, a second mains switching module and a battery switching module. The rectifier discharge reuse module includes a filtering unit and a rectifier discharge unit that are connected to each other; the battery switching module is connected between a battery power supply and the filtering unit, and operates in a case that the battery power supply supplies power to the rectifier converter; and the first mains switching module is connected between a mains power supply and the filtering unit, the second mains switching module is connected between the filtering unit and the rectifier discharge unit, and the first mains switching module and the second mains switching module operate in a case that the mains power supply supplies power to the rectifier converter.