This study was undertaken to examine feasibility of biological treating of landfill leachate that was collected from Tehran municipal landfill with about 0.5 – 1 year old. Average COD of the leachate in aerobic submerged membrane bioreactor is 68000 mg/L. The reactor with a working volume of 175 L, having membrane module (Hollow fiber) with pore size of 0.1 µm was used in this study. The dissolved oxygen concentration (DO) was maintained at 3.2 mg/L and solid retention times (SRTs) and hydraulic retention times (HRT) were controlled at 55 and 15 days respectively. Following that the mixed liquor suspended solids (MLSS) was stabilized at 6.3 g/l. Under condition of COD/N ratio of 46 and COD/PO4-P ratio of 455 and BOD/COD ratio of 0.65, the average effluent COD was 1733 mg/L with average removal efficiency of 97.46%. The average NH 4 –N removal efficiencies was 99% which was reached to 99.7% at maximum level.