NOVELTY - Treating biodiesel production process waste water comprises evaporating and concentrating waste water by a triple-effect evaporator, cooling, passing into a buffer tank, separating surface oil slick, transferring into a vortex concave air flotation machine, allowing the residual suspended substances to subsequently enter into a hydrolysis acidification tank, biological contact oxidation tank, secondary sedimentation tank, water biological aerated filter (BAF), sand filter tank, tubular sterilization device, clean water recycling tank and sludge concentrating tank and dehydrating.    USE - The method is useful for treating biodiesel production process waste water (claimed).    ADVANTAGE - The method uses three-effect evaporator, which saves energy; and carries out deep processing with aeration biological filter tank and sand filter tank, thus ensuring closed circulating waste water and zero discharge waste water.    DETAILED DESCRIPTION - Treating biodiesel production process waste water comprises (a) evaporating and concentrating the salt-containing waste water by a triple-effect evaporator, cooling water through a heat exchanger, allowing the circulating water to enter into a buffer tank after cooling, mixing the oily waste water after oil separation, separating the surface oil slick, transferring the waste water into a vortex concave air flotation machine, where the air flotation machine allows generation of bubbles on the surface, and tiny bubbles are produced after the release of dissolved air, allowing the residual suspended substance and oil to the sludge tank from the air flotation machine, discharging clean water into the buffer tank, and uniformly mixing salt waste water and circulating water, (b) pumping the waste water from the buffer tank to a hydrolysis acidification tank via a pump, allowing the decomposition of macromolecular and micromolecular organic substances in the waste water, and removing 30% chemical oxygen demand (COD), (c) allowing the hydrolysis acidification tank effluent to enter into the biological contact oxidation tank, to remove organic substances by aerobic microorganisms, removing ammonia nitrogen by nitration and denitrification, (d) discharging the biological contact oxidation tank effluent into a secondary sedimentation tank, allowing the effluent of the secondary sedimentation tank into water biological aerated filter (BAF), allowing the effluent of BAF into the sand filter tank, filtering in the sand filter tank to remove suspended solids (SS) the waste water, taking a tubular sterilization device, and discharging into a clean water recycling tank, and (e) processing the resulting oil separation adjustment tank, vortex concave air floatation machine and secondary sedimentation tank sludge and scum into sludge concentrating tank, transferring into a horizontal screw centrifugal machine for dehydration, and discharging the dry sludge.