The discharge percussion welding is available for joining miniaturized components difficult to weld by conventional method. But the defect of this welding method is that the breaking strength of welded work pieces frequently fluctuates largely. In this report, the causes for this fluctication of weld strength areshown. The results are as follows. If the weld runs on the condition below a comparatively low loading voltage and a small capacity of condensor, the breaking strength fluctuates by incomplete weld occuring from the unstability of sparking ignition gap distance and sparking time duration, which respectively change largely by atomospheric condition, surface condition, and percussive velocity. But, if the weld runs on the condition over a sufficient high loading voltage, and a large capacity of condensor, the breaking strength reaches to normal and comparatively stable one. Accordingly, for industrial purpose, a loading voltage as low as possible, and a capacity as small as possible, among the stable welding region must be applied to the discharge percussion welding, because thin rod pieces melt off, or deform by too much heat generated.