The invention provides an uninterrupted power system, which comprises a power converter, an inverter, an energy storage battery and an energy management system. The power converter is connected withthe commercial power, a load and the energy storage battery. The inverter is connected with the load and the energy storage battery. The energy management system is used for carrying out different control on the power converter and the inverter when the SOC state of the energy storage battery, the power supply state of the commercial power and the current time meet different preset conditions so as to uninterruptedly supply power to the load. The energy management system controls the power converter and the inverter, so that the energy storage battery can supply power to the load independentlywhen the commercial power is off, the energy storage battery and the commercial power can supply power to the load at the same time, and the utilization rate of the energy storage battery is increased; and since the energy storage battery is often in a charging and discharging state, the service performance and the service life of the energy storage battery are improved.