The present invention is to provide a voltage regulator circuit disposed on a circuit board of a blade server including a voltage regulator module for converting voltage of a power source and outputting the power source and a switch unit being connected with the voltage regulator module, wherein a standby power source output end disposed between the voltage regulator module and the switch unit is able to continuously output power sources as standby power sources to each of components on the circuit board when the switch unit is opened. When the blade server is turned on and the switch unit is closed, a power source output end of the switch unit will output the power sources as standard powers to each of the components, meanwhile, the standby power source output end is still outputting the standby power sources.