Continuous upflow anaerobic sludge blanket reactor performs more favorably at the higher organic loading rate than other anaerobic treatment. The treatment of municipal landfill leachate of Shiraz’s city investigated using continuous flow anaerobic reactor and subsequently aerated lagoon. Landfill leachate has chemical oxygen demand of 45,000–90,000 mg/L and ammonia nitrogen at 1,000–2,500 and heavy metals that can impact biological treatments. Capacity of anaerobic and aerobic reactors is 10 and 20 L that operated at detention time of 2 and 4 days, respectively. Organic loading rate of upflow anaerobic sludge blanket is between 0.5–20 g chemical oxygen demand/L/day. Chemical oxygen demand removal efficiencies are between 57–87, 35–70 and 66–94% in the anaerobic, aerobic and whole system, respectively. As the entry, leachate organic loading rate increased from 1 to 20 g/L/day, the chemical oxygen demand removal efficiency reached a maximum of 71% and 84% in the anaerobic reactor and whole system, respectively, at high organic loading rate. Ammonium removal efficiency was about 54% after the aerobic stage.