A power good signal generating circuit includes a first resistor and a capacitor, a system power is grounded via the first transistor and the capacitor in sequence; a first transistor, the base of the first transistor is for receiving a PS_ON signal from the motherboard, the collector of the first transistor is connected to a node between the first transistor and the capacitor; a second transistor, the gate of the second transistor is connected to the collector of the first transistor, the drain of the second transistor is connected to a standby power; and a third transistor, the base of the third transistor is connected to the drain of the second transistor, the collector of the third transistor is connected to the system power, for outputting a PWR_GOOD signal.