Particulate matter (PM) produced from poultry production facilities may strongly affect the health of animals and workers in the houses, and PM emitted to the ambient air is an important pollution source to the surrounding areas. Aviary system is considered as a welfare friendly production system for laying hen. However, its air quality is typically worse as compared with conventional cage systems, because of the higher PM concentration of indoor air and other airborne contaminants. Furthermore, PM physical property, which has a direct impact on the penetration depth into the lungs of the birds and humans, is largely unknown for the aviary system. Therefore, a systematic method was utilized to investigate the characteristics of particles in aviary house with large cage aviary unit system (LCAU) in Beijing, China. For the field measurements, three measuring locations were selected with two inside and one outside the house with LCAU to continuously monitor PM concentrations and collect the samples for particle size distribution (PSD) analysis. Results showed that PM, PM and total suspended particulate (TSP) concentrations averaged at 0.037 ± 0.025 mg/m, 0.42 ± 0.10 mg/m and 1.92 ± 1.91 mg/m, respectively. Particle concentrations increased from October to December due to less ventilation as the weather getting colder, and were generally affected by stocking density, ventilation rate, birds' activities and housing system. Meanwhile, indoor PM concentration was easily impacted by the ambient air quality. Mass median diameter (MMD) and mass geometric standard deviation (MGSD) of the TSP during the measurement were 18.92 ± 7.08 μm and 3.11 ± 0.31, respectively. Count median diameter (CMD) and count geometric standard deviation (CGSD) were 1.94 ± 0.14 μm and 1.48 ± 0.08, respectively. Result indicated that the aviary system can attain a good indoor condition by suitable system design and environment control strategy.