Started from the analysis on factors influencing the small hole electron discharge machining (EDM) processing speed, the change of working liquid conductivity so as to change the discharge gap and to optimize chips removal conditions, and the theory to improve the EDM at a high speed were researched. By small hole EDM experiment with different additives to change the working fluid conductivity, compared with the processing speed of the original running water working fluid, there is found a certain relationship between the working fluid conductivity and hole processing speed, that the best working fluid conductivity range is existed. The conclusion obtained on small hole of EDM machining working liquid ratio has certain reference significance. 