脈衝電化學加工〈PECM〉是利用有規律的間歇供電進行間歇加工。而空隙分數是影響加工品質的重要因素之一。本實驗使用透明壓克力模具模擬流場場區，以氯化鈉水溶液作為電解液，並藉由控制脈衝頻率及電場、熱流場等參數，分析各參數對空隙分數〈Void Fraction〉的影響度。 實驗結論指出，影響空隙分數的氣泡層厚度隨著脈衝頻率減少而減少；而增加電壓、增加電解液濃度或降低流速會使氣泡層增厚。因此加工時若能配合固定電壓與濃度並控制電解液流速則可找出脈衝頻率與電解液流速的最適化條件進而有效降低空隙分數，提高產品生產品質。 In the pulse electrochemical machining (PECM) a regular intermittent power is used to machine the product intermittently. However, the void fraction is the key factor for the product’s quality. In this experiment, a clear acrylic module is used to simulate the fluid field where the sodium chloride solution is chosen as the electrolyte. The pulse frequency, the electric field related parameters and thermal flow field related parameters are controlled to analyze the influence of parameters the void fraction. Results show that the thickness of the boubble which effects the void fraction would decreases as the pulse frequency decreases. On the other hands, the thickness of the bubble increases as the voltage increases, the electrolyte concentration increases or the electrolyte flow speed decreases. Therefore, by fixing the voltage and concentration and well controlling the electrolyte flow speed, a optimal condition between the pulse frequency and the electrolyte flow velocity can be achieved. In turn, the void fraction decreases and the product quality is thus improved effectively.