The present invention mainly relates to a voltage regulator, comprising: a P typed power MOS; a feedback circuit; a differential amplifier; a protecting circuit having a N-typed transistor current mirror; and an active foldback current limiting circuit rather than using a resistor. When the P typed power MOS is under short circuit current situation, the current at the output side of the current mirror is increased in order to limit the current flown through the power MOS. Meanwhile, the same purpose can also be served by increasing the current at the input side of the DC current mirror.