Abstract: Effluent from anaerobic digesters, which contains high ammonium concentration and with low C/N ratio, can not be treated effectively by using traditional biochemistry methods. In this study, ammonia stripping was used to decrease ammonium concentration in effluent from anaerobic digesters of piggery wastewater. Influences of initial ammonium concentration, pH value, air flow to liquid flow ratio, temperature on ammonia removal rate were studied. The coagulation effect of Ca(OH)2 was further explored. The results showed that the initial ammonium concentration of 500 or 900 mg/L had no significant difference on the ammonia removal rate; Ammonia removal rate could achieve 81.84% at the experiment condition with initial ammonium concentration of 900 mg/L, pH value of 10.5, air to liquid ratio of 2000, and temperature of 30℃. A dose of Ca(OH)2 5 g/L performed a good coagulation effect, the removal rates of COD TP and PO43- were 30.13%, 97.44% and 98.76%, respectively, but the hardness increased by 106%. The results can provide a reference for the development of advanced treatment of biogas plant effluent.