The invention discloses a method for improving the safety and energy-efficient performance of a civilian electrical appliance, and an energy-efficient civilian DC power supply system. The power supply system comprises a DC power supply device, a constant voltage/current circuit, a DC load, an automatic load detection circuit and a control module, wherein the output end of the DC power supply system is connected with the input end of the constant voltage/current circuit; the output end of the constant voltage/current circuit is connected with the DC load; the automatic load detection circuit carries out real-time sampling on the voltage and/or current of the DC load and inputs sampling signals to the control module; the control module judges the load change of the DC load according to the input sampling signals and outputs PWM pulse signals to the constant voltage/current circuit according to the judgment results; and the constant voltage/current circuit adjusts the output power into an output power meeting the DC load requirement according to the received PWM pulse signals. The method and the system have the advantages of energy saving, safety, wire rod saving and low cost.