In this research, the effect of intermittent feeding on the efficiency of plug flow activated sludge reactors has been studied. An experimental plant has been constructed and operated. The plant consists of five identical reactors with the volume of (15) liter working in parallel under the same operating conditions for each of discharge; sludge recycling ratio; hydraulic detention time and the organic load. Four of these reactors had been worked at the intermittent (ON/OFF) feeding mode with the ratios of (1/1), (2/2), (4/4) and (6/6) for the first, second, third, and fourth reactor respectively, while the fifth reactor worked at continuous feeding mode. The results showed that, removal efficiencies for each of ammonia (NH3) and phosphorus (PO4) were close in both of intermittent and continuous feeding system, while the concentrations of (COD) in effluent were less in the intermittent reactors. Removal efficiencies of (COD), (NH3), and (PO4) decreased with reducing the hydraulic retention, whereas nitrate removal efficiency increased with decreasing of hydraulic retention time.