A new method of electrical discharge machining ( EDM ) in air-mixed medium-air-mixed EDM was presented, and comparative experiments were carried out to compare the machining characteristics of air-mixed EDM with conventional EDM. The experimental results showed that better machining performances were obtained with tool electrode as the cathode and workpiece as the anode. It was found that the material removal rate(MRR) was higher, the tool electrode relative wear ratio (TWR) was lower and the surface roughness (SR) quality was better in the case of air-mixed EDM than that of conventional EDM, and the reasons bringing out the results were analyzed.