Ultra-filtration is an advanced technology to separate, purify and concentrate substance . lt presents hollow capillary tube shape or hollow fiber shape, micro-pore covers tube wall densely.Feed liguid is flowing in or out the membrane under the influence of pressure, dissolvent or smalmolecule can permeate membrane and become pure liquid by collection, while large molecule(such as protein, each kind of enzyme, nucleic acid, polysaccharide and so on) ,colloid particle(such as emulsion, micro-ion) and bacterium are cut off by the membrane and are taken off bythe circulating liquid flow to become concentrating liquid.