With the increasing scale and intensive production of the livestock and poultry breeding industry, more and more attention has been paid to ammonia emission reduction from the animal farm. Ammonia discharged directly into the atmosphere would combine with SO2 or NOx to form secondary particles which can reduce atmospheric visibility. Moreover, the NH3 emission is related to the risk of environmental problems such as soil acidification and water eutrophication. Ammonia is the stench gas emission in farms as one of the major pollutants in farms. Emission control of farm ammonia is an important part of air pollution control. There is a big gap in the research and application of environmental protection unit and automatic control system between our country and abroad. Biomass removal technology has attracted more and more attention due to its advantages of high efficiency, no secondary pollution, good safety, simple equipment construction, easy operation and maintenance, and low cost. A pilot ammonia bio-oxidation device based on the biological principle and PLC control was set up in a pig farm in Beijing. It realized the automatic storage and adjustment of pH value, the ventilation control, the real-time measurement and curve display of environment parameters in the bioreactor. After the system in pig farm was running stable, longterm test and continuous test were adopted to detect the treatment effect of ammonia oxidation device. After two-month operation, the ammonia removal efficiency could reach up to 90%. The device has the advantages of stable and reliable operation, together with low operation cost.