Abstract: Based on special characteristics of mine-used 2-quadrant frequency converter and analysis and calculation of ripple current and ripple voltage of DC-link capacitor of frequency converter, a simple and easy selection method of DC-link capacitor was presented from point of current flows of inverter side. The correctness of the method was proved by use of Simulink software. At last, it illustrated film capacitors is superior to electrolytic capacitors as DC-link capacitor of frequency converter.