Abstract: An experiment of the chemical industrial park wastewater treatment by flat MBR system got excellent treatment effect. The removal rates of COD and NH3-N were over 95% and 99% respectively. The MLSS in this MBR system kept stable at 8200 mg/L，the SS of treated water was almost 0，all the indexes reached the Chinese standard of reclaimed water (GB/T 18920—2002). This experiment result showed that the flat MBR system had the advantages of simple process，small land occupancy，high efficiency，and good treatment result. An economic analysis showed that the unit treatment cost of flat MBR was only a little higher than Cyclic Activated Sludge System (CASS). It is a good way for the chemical industrial park to take wastewater into recycle，save resource and reduce pollution.