A method using force commutated reactive power compensator to compensate for the fundamental reactive power of source and to raise the power factor of source is introduced.A new type of four quadrant converter is designed and the analyses of current commutate during the thyristor commutate is presented.The design and the lab installation with microcomputer control system are described.It is proved through experiment that the presented method can fully compensate for the fundamental reactive power of source and can also improve current waveform.