In this study, an electrolytic micro-machining tester is employed to investigate the effects of supply voltage,electrode gap and initial machining position on the geometry of the tungsten needle. The tungsten needle to be electrolyzed is dipped in an aqueous electrolyte of 2wt % sodium hydroxide as the anode, and the stainless steel needle with a diameter of 50 £gm as the cathode(tool electrode), and the electrode gap is set to be 30 £gm.Morever,the tungsten needle can be allowed to be fixed or in the reciprocating motion. Experimental results show that when the tip diameter of stainless steel needle is less than 50 £gm, a great quantity of current density and power are generated to cause the temperature failure of the tool electrode. At a certain gap between the electrodes, the electric field is focused on the narrow range to improve its processing efficiency. Under the higher supply voltage condition, it is difficult to control the size because the diameter of tungsten rod is reduced very quickly. Under the lower supply voltage condition, the diameter of tungsten rod can be processed to smaller sizes, but it takes a long time. Therefore, in the beginning of the experiment, the tungsten rod is electrolyzed under a higher voltage to the small size, and then the supply vltage is switched to lower value to conduct the electrolysis process. Consequently, a finer and more even tungsten needle can be obtained. Experimental results show that a more even tungsten needle with the length of 600 £gm and the diameter of 4 £gm can be manufactured.