Experiments of single pulse electrical discharge of various materials and various parameters were carried out on the Experimental Setup homemade. The values of gap voltage and current waveform were recorded and conserved by the digital storage oscilloscope in the experiments under different conditions. The results consider that, although the discharge waveform of electrical discharge machining (EDM) of Polycrystalline Diamonds is similar to the general EDM, but its breakdown voltage, maintain voltage of spark and characteristics of short circuit waveform are different obviously from that of general EDM.