Evaporation was applied to concentrate biogas slurry. The effects of low temperature evaporation, atmospheric evaporation and vacuum evaporation on biogas slurry concentration were investigated. Results showed that the low temperature evaporation (room temperature, 25℃, 35℃, 45℃, 55℃, 65℃, 75℃, 85℃) had a great impact on the ammonia nitrogen concentration of biogas slurry, and almost all ammonia (98%) were lost, which has disadvantages on the recovery of nutrients. It showed that when the initial pH value was less than 4 in atmospheric evaporation, the water quality of the effluent (ammonia is lower than 41.0mg/L) could meet the demand of Discharge Standard of Pollutants for Livestock and Poultry Breeding (GB18596—2001). Experimental results of the vacuum evaporation showed that vacuum degree（-0.03～-0.08MPa） had little influence on evaporation results. Vacuum evaporation of biogas slurry with different initial pH value showed that compared with the atmospheric evaporation, vacuum evaporation could reduce the content of ammonia nitrogen and chemical oxygen demand (COD) in effluent and improve quality of effluent. When the initial pH value of biogas slurry in vacuum evaporation process was less than 5, the effluent (ammonia is lower than 61.8mg/L) could meet the discharge standard. Therefore, the most effective operation for the whole system is vacuum evaporation.