Summary form only given. Pulse-modulated RF atmospheric pressure discharges were investigated in recent years to reduce the thermal accumulation of the discharge and extend the operation region of the stable apha glow mode. Different pulse-voltage and current waveforms were acquired in previous experiments, but no attention was paid to the interpretation. We investigated this issue by the aid of positive and negative feedback effects deducted by varying the series capacitor in the inversely L-shaped matching network employed in our pulse-modulated RF atmospheric pressure discharge. The evolution of the RF pulse is found to be influence by the igniting voltage and the feedback effect, as a result, a variety of waveforms present by igniting the discharge in the rising edge or the plateau, and the positive or negative feedback region. The spikes or the bird-heads of the pulsed waveforms appear in the negative feedback region. The pulse undershot in final stage of the spike could be substantial that the RF discharge extinguished within a time interval and subsequently re-ignited. The positive feedback region is relatively narrower, and the pulsed RF discharge originally ignited in the positive feedback region can develop into the negative feedback region.