A power supply circuit for a PCI-E slot includes a control chip, a first electronic switch, and a second electronic switch. The control chip determines a status of a motherboard, outputting a control signal. A first terminal of the first electronic switch is connected to the control chip to receive the control signal, and connected to a +3.3V dual power supply of the motherboard through a first resistor. A second terminal of the first electronic switch is grounded. A third terminal of the first electronic switch is connected to a first terminal of the second electronic switch, and connected to the +3.3V dual power supply through a second resistor. A second terminal of the second electronic switch is connected to the +3.3V dual power supply. A third terminal of the second electronic switch is connected to a PCI-E slot.