Abstract: Abstract: The ammonia (NH3) and particulate matter (PM) emissions from livestock farming have been an important issue for influencing the animal health and social environment. Among the different livestock categories, the layer production has been proven to have higher NH3 and PM emission potentials when compared with cattle or pig rearing. Also, with the increasing demand of egg protein due to urbanization during these years in China, layer production has become an important industry in North China region, causing the layer production to be an important NH3 and PM emission source in this region. However, with the upgrade of livestock house structure and farm management, also the deeper knowledge of PM hazard on health, as well as the high intention on the relationship between the NH3 emission and the haze event, the former monitoring information of NH3 and PM emissions in livestock house can't meet the urgent demand for evaluating and mitigating of the livestock NH3 and PM emissions nowadays. In this study, the NH3 and PM emissions (including PM2.5, PM10 and total suspended particulates (TSP)) from a typical large scale cage layer house (100 000 birds per house) in suburb Beijing were monitored for a consecutive eight days during winter, and the NH3 and PM emission fluxes were estimated based on carbon dioxide balance method. The results showed that, the average NH3 concentration of the air outlet from the layer house was (4.58±3.29) mg/m3, and the NH3 emission flux per bird was (32.2±12.5) mg/d. The PM2.5, PM10 and TSP concentrations of the air outlet were (0.13±0.06), (0.81±0.16), (3.28±1.32) mg/m3, respectively; while the emission fluxes per bird were (0.7±0.4), (6.3±1.4), (27.6±12.5) mg/d, respectively. The NH3 and PM emissions of the layer house showed an emission trend of a two days cycle, which was in accordance with the two days manure clean frequency indoor. The indoor TSP and PM10 concentrations during the daytime were obviously higher than those of nighttime. In the days with manure belt cleaning, the concentrations of TSP, PM10 and PM2.5 during daytime were 5.6-7.1, 3.2-4.2 and 5.6-6.3 times as much as that during nighttime, respectively; while in the days without manure belt cleaning, the concentrations of TSP, PM10 and PM2.5 were 2.1-2.4, 1.8-2.4, and 0.8-2.2 times as much as that during nighttime, respectively. Besides of the manure cleaning manipulation and the layer activity during daytime, the indoor PM2.5 concentration was influenced by the ambient air PM2.5 conditions to some extent, causing the PM2.5 concentration during daytime couldn't always be higher than that during nighttime, especially when the haze event suddenly occurred during nighttime. The ratio of PM2.5 to PM10 of the air outlet was 10.4%～20.4%. The K+, Mg2+ contents of the PM2.5 in the air outlet were significantly higher than those of the ambient air PM2.5(P <0.05). For the particle ion balance of the PM2.5 from the air outlet and the ambient air, the analyzed cations were higher than anions. The results of this study can provide a scientific basis for compiling the NH3 and PM emission inventories for livestock industry; also the analysis for the PM elements can provide basis for studying the formation mechanism of secondary inorganic aerosols and PM source apportionment.