Aims: Feasibility of the anaerobic migrating blanket reactor (AMBR) was investigated for the treatment of composting leachate. Materials and Methods: The AMBR consisted of a rectangular, plexiglas reactor (inside dimensions: length = 43 cm, height = 23.5 cm, width = 10 cm) with an active volume of 10 L. which divided reactor into four identical compartments (2.5 L). Composting leachate was used as a feed. Start-up of a reactor with diluted feed of approximately 10.43 g/L. Chemical oxygen demand (COD) was accomplished in about 44 weeks using seed sludge from the anaerobic digester of municipal wastewater treatment plant and operated continuously at mesophilic phase. The organic loading rates (OLRs) applied to the system was gradually increased from 1 to 19.65 g COD/L.d. Results: The reactor with hydraulic retention time of 10 day at 35C and initial OLR of 1 g COD/L.d showed 82.3% COD removal efficiency. The best performance of the reactor was observed with an OLR of 3.79 g COD/L.d. In influent of reactor, BOD 5 /COD ratio, TSS, VSS and TDS were ranged from 0.47 to 0.69, 1650 to 16,830, 990 to 12,622 and 2630 to 31,240 mg/L and in effluent of reactor were reached to 0.28 to 0.38, 660 to 7452, 346.5 to 4597 and 1860 to 19,490 mg/L, respectively. Conclusion: The AMBR could be an appealing option for pretreatment of organic load in composting leachate and improving the efficiency of the next biological reactors.