This paper presents an implementation of a DSP- based shunt active power factor corrector (PFC). The working principle of four-switch series-connected PFC is introduced. To examine the actual circuit characteristics, MATLAB/Simulink is used to implement circuit of shunt active PFC and analyze the relations between the load, VE DC voltage, source voltage and current. Analysis of circuit of the digital shunt-connected active PFC includes main circuit diagram and control circuits, such as adders, voltage converters, electric current sensors, feedback circuits and hardware circuit structure, calculation of main circuit inductance and design of capacitance value. Based on the control rule of source current slope, the relation between output capacitance voltage of the single-phase shunt PFC and source current waveform distortion is discussed. Finally, the influence of the efficiency with fixed capacitor voltage is shown in the experiment result.