The invention provides a voltage regulator including a voltage divider and a power supply. The voltage divider circuit includes a first, second, third PMOS transistors, a first NMOS transistor, a pull down circuit, and a switching capacitor circuit. The pull down circuit includes a plurality of switches controlled by a pull down control signal. The switching capacitor circuit controlled by a first control pulse includes a capacitor and provides the capacitor connected to the dividing voltage for a short period while the power supply starts up to provide the input voltage. The power supply includes a comparator and a power voltage switch. The comparator compares the dividing voltage and a reference voltage and outputs a comparison result correspondingly. The power voltage switch is controlled by the comparison result to provide the input voltage from a power voltage.