Abstract: The water pollution was increasingly serious recently in China, and the rural sewage pollution accounted for high proportion. The up-flow biological aerated filter (UZBAF) with inner diameter of 185 cm and with 54 L of built-in natural zeolite filter sand was used in the demonstration base for harmless treatment of rural sewage. The results showed that under the conditions of hydraulic loading 2 m³/h and residence time 1.0 h, when the gas-water ratio increased from 2∶1 to 4∶1, COD_Cr average removal rate increased from 75.2% to 83.4%, BOD₅ removal rate increased by 5.9%; turbidity removal rate increased from 91.9% to 94.8%, NH₄⁺-N average removal rate increased from 82.6% to 98.1%, NH₄⁺-N average concentration of the effluent fell from 3.3 mg/L to 0.28 mg/L; the removal rate of TN, TP, alkalinity and conductivity was 56.2%, 26.7%, 27.5% and 10.8%, respectively; and the removal rate of bacteria and ascaris eggs was 99.9% and 100%, respectively. The effluent could reach the target of the first-grade discharge standard of Synthetical Draining Standard of Sewage (GB 8978-1996). It was concluded that under the conditions of hydraulic loading 2 m³/h and residence time 1.0 h, UZBAF devices could realize harmless treatment of rural sewage.