A motherboard power on circuit includes a switch connector, an impedance circuit, and a super I/O chip. The impedance circuit includes a first resistor, a second resistor, and a capacitor. A terminal of the first resistor is connected to the power on terminal of the switch connector. The other terminal of the first resistor is connected to the power on terminal of the super I/O chip, a terminal of the second resistor, and a terminal of the capacitor. The other terminals of the second resistor and the capacitor are connected to a power source and ground respectively.