The invention provides an electronic device power supply circuit used for provding stable voltage for a first working module of the electronic device. The circuit comprises a power source, at least one boost module, a voltage comparison module, a first switch, a second switch and at least one first step-down module. The power source is electrically connected to the first working module by the first switch and the first step-down module. The boost module is electrically connected to the power source and is also electrically connected to the first step-down module by the second switch. The voltage comparison module is electrically connected to the power source and the first switch as well as the second switch. The comparison module is used for monitoring the output voltage of the power source to control the switching of both the first switch and the second switch. The electronic device power supply circuit of the invention switches off the first switch and switches on the second switch in the case of a sudden voltage loss. The boost module boosts the output voltage of the power source and provides the output voltage to the first working module; as a result, crash machine caused by lack of voltage in the first working module can be effectively avoided. In addition, the invention also provides a power supply method.