The DC-side capacitor voltage of shunt active power filter (SAPF) has direct influence on the performance of the harmonic compensation. A reasonable setting value of the capacitor voltage can guarantee the compensation effect and reduce the voltage value of the DC-side capacitor. Aiming at the problem of design and optimization of DC-side capacitor voltage, through the analysis of the current under the typical load condition, the output voltage vector of the converter is derived when the harmonic current is fully compensated. Based on the space vector pulse width modulation (SVPWM), the selection method of DC-side capacitor voltage is analyzed. Simulation results confirm the validity of the method. This work is supported by National High-tech R & D Program of China (863 Program) (No. 2015AA050104).