The control strategies for series converter of three-phase four-wire unified power quality conditioner（UPQC） are investigated. With the help of the individual control of the input currents of the series converter in the ABC coordinates to transfer the series converter into a sinusoidal PWM current source， the three-phase currents under the non-sinusoidal and unbalanced supply voltages can be sinusoidal and balanced waveform. The voltage unbalance between the two group capacitors connected into the direct current bus is also eliminated. Experimental results verify the validity of the control strategies in governing the power quality and in improving the operation performances of parallel converter.