Pure wood vinegar is widely used in industry, agriculture and other areas as regulators, but the wood vinegar which produced usually is filled with oil on the surface .The paper mainly study on removing the floating oil on the surface of wood vinegar,choosing the best surfactant called Tween 80 to removing the floating oil and making wood vinegar in a steady system. By this way, it will not appear oil on the surface of wood vinegar for more than half an year, which will broaden the commercial application of wood vinegar