UF ultrafiltration apparatus outlined electrophoretic paint, the electrophoretic fluid pressure system through the membrane tube made of special materials, the filter apparatus in the paint resin with water, the solvent and the dissolved metal impurities separation. Ultrafiltration is the continuous phase (water + dissolved impurities include dye solution + salts) and the dispersed phase (resin and pigment) separation process, the separation process can also be said that the organic phase in the aqueous phase. The aqueous phase through an ultrafiltration membrane due to so called "permeate" permeate contains some solvent, all the water-soluble ionic impurities and some low molecular weight resins. There are many support film material tubule ultrafiltration membrane tube. When these tubules by electrophoretic paint, and some of the water phase through these tubules, the outflow ultrafiltration unit, the resin and macromolecular electrophoresis tank effluent filter tube is returned. For electrophoretic paint ultrafiltration machine has four functions: 1. to remove impurities rapidly reduce the conductivity 2. 3. The working liquid electrophoretic paint accelerate new solution was aged and control the content of the solvent in the use of electrophoretic paint recovery 4. impurity ultrafiltration machine is the most important feature, because most of the contaminants is the formation of soluble salts into the working fluid. They harm the working fluid, most anions (especially hydroxide and chromate) is easy to form a precipitate with paint: paint anion will reduce the deposition rate of the workpiece surface and paint appearance deteriorated. Ultrafiltration function effectively remove these contaminants from the purification. Electrophoresis was not excessive ultrafiltration, otherwise it will lose the main parts of electrophoretic paint and lower solvent content and changing the acidity of the electrophoretic paint. Only with a new electrophoretic paint, the excess before ultrafiltration to remove excess solvent and a small molecule compound.