The invention discloses an integrated asynchronous excitation phase modifier and a reactive compensation and active balance method thereof. The phase modifier comprises a three-phase AC excitation winding, a voltage source type inverter, a super capacitor and a voltage source type rectifier, wherein the super capacitor is used for providing energy for the voltage source type inverter and maintaining a voltage level of the voltage source type inverter, the voltage source type rectifier is used for absorbing active power from a power grid side, converting AC current of the power grid side into DC current, providing active power for the super capacitor and the voltage source type inverter and transmitting reactive power to a power grid, and the voltage source type inverter is used for inverting the DC current transmitted by the voltage source type rectifier into a three-phase AC excitation current needed by a three-phase rotor excitation winding. According to the phase modifier and the method thereof, through controlling a rotation speed of a rotor, the phase modifier is made to absorb superfluous energy of the power grid when lines are in short circuit fault partially, relatively strong inertia is realized, safety and stability of the power grid are facilitated, and reactive compensation capability and transient performance are better.