Against to the characteristics of sewage in Ping Fang-wang oilfield, we had independently researched and developed a multiple-function ultrafine apparatus. Following the principles of gas-liquid distribution and mass transfer in multiphase flow, the apparatus can mix a certain amount of air to the sewage, modified the sewage by the pre-oxidation deferrization and desulfurization process, dealing with the problems of corrosion and instability of sewage quality in the treatment station at the same time. The field test result shows that, it is obvious to remove the CO₂ by above 65%, sulfur by 100% and ferri by above 90% in the pre-oxidation process, and raise the pH value by 0.9. So it is worth of being spread in sewage treatment.