Abstract: The design capacity of the upgrading and extension of a wastewater treatment plant(WWTP) from Danjiangkou was 3.0×10⁴ m³/d. Main indicators of the effluent quality met the class Ⅳ criteria in Environmental Quality Standard for Surface Water and TN concentration was less than 15 mg/L. A²/O(anaerobic/anoxic/oxic process)+MBR(membrane bioreactor) combined process served as the secondary treatment and realized the designed target with good treatment performance. The application of BIM(building information modeling) technology was introduced in combination with the design of MBR process, and the optimization proposal to the potential problems was provided based on the analysis results. Meanwhile, the solutions to some problems exposed during the practical operation were presented as well, such as the layout and lifting of the devices, sludge sedimentation and aeration, cavitation projection of reflux pumps, which could provide reference for the similar projects.