Both immersion fluid and spray liquid cooling methods were used in high speed wire-cut electrical discharge machining(HSWEDM) experiments. The results show that with the same processing parameters, the cutting speed of immersion fluid is lower than that of spray liquid. A primary cause of this is the continuous leakage current of electrolytic between the work-piece and wire electrode which covered with electrolyte liquid. The relationship of the discharge energy loss and the leakage current between electrolyte liquid and the leakage current of work-piece were analyzed. The experimental results show that by reducing the surface leakage current area of the work-piece and working fluid conductivity, the energy loss could be effectively reduced, and the processing efficiency could be improved.