Abstract: Ammonia (NH3), as the only reactive alkaline gas, plays a crucial role in the neutralization of atmospheric sulfuric or nitric acid to generate ammonium salts, thereby affecting the acidity of cloud water and aerosols. At present, the ammonia emissions which is the main component of fine particulate (particulate matter equal to or less than 2.5 μm in aerodynamic diameter; PM2.5), has become a global hot issue. Livestock and poultry breeding is the main emission source of ammonia, and the total amount of ammonia released by China's pig industry is much higher than that of Europe and North America. An in-depth study about ammonia emission from livestock sources may help policy-makers to develop emission reduction scheme and ease the haze. Generally, pig is considered to be the major contributor to ammonia emission. Therefore, in this study, we investigated NH3 emissions from a pig farm in Yangtze River delta region which were equipped with typical mechanical ventilation system and manure collection system cleaning by rising water. It monitored the ammonia emissions from different houses at the same time which included different growth stages of the fattening pigs and sows (among them, the fattening pigs can be divided in three phases according to the weight, Nursery (<24 kg), and Fattening-I (24-60 kg) and Fattening-Ⅱ (60-120 kg).The sow can be divided into Gestation and Farrowing, and the ammonia emission flux was determined. Meanwhile, in this study, we analyzed the ammonia emission characteristics to explore the contribution of ammonia emissions in different growth stage. The results showed that the NH3 concentrations of Nursery, Fattening-Ⅰ, Fattening-Ⅱ, Gestation and Farrowing were (0.97±0.4), (3.37±0.70) and (5.45±2.30), (2.19±1.06) and (1.44±0.48) mg/m3, respectively. The ammonia emission in each column had a significant daily change process. In the morning, the ammonia discharge were fluctuated and increased, then started to decrease in the afternoon, and the value kept low at night. The ammonia emission rate was significantly positively correlated with the temperature and was negatively correlated with the humidity. The daily NH3 emissions rate of Nursery, Fattening-Ⅰ, Fattening-Ⅱ, Gestation and Farrowing were 0.85, 6.53, 8.20, 10.39 and 13.86 g/(pig•d). In fattening pigs, the contribution rate of Nursery, Fattening-Ⅰ, Fattening-Ⅱwere 3.64%, 26.11% and 70.25%. In sows, the contribution rate of Gestation and Farrowing was 75.32% and 24.68%. Artificial disturbance, such as feeding and defecation, increased the ammonia emission in the pig houses. The ammonia emission rate of sows was 1.87 times higher than fattening pigs. By monitoring the concentration of ammonia emission from fattened pigs and sows at different growth stages, we explored the characteristics of ammonia emission from large-scale pig farms, discriminated and analyzed the important influencing factors of ammonia emission, and discussed the contribution of fattened pigs and sows of different types to ammonia emission during growth stages to provide technical support for the accounting of ammonia emission in regional livestock and poultry breeding. These findings in this paper could be useful for estimation of ammonia emissions accurately and implementation of ammonia emission reduction measures in China.