Abstract: Abstract: With the intensive introduction of policies and acts for environmental protection, the farming land shortage situations for domesticated animals are increasingly serious. Innovational multistory pig buildings are introduced to save land resources and thus increase breeding intensities. The following awareness and concerns towards air qualities of animal occupant zones on each floor are being raised among pig producers. In this paper, a wireless sensor network for collecting environmental factors was used to monitor the thermal environments and harmful gases of three representative floors in multistory pig buildings, which were the top floor (7th floor), the middle floor (5th floor) and the ground floor (1st floor). According to the heads of animals and their weights on these representative floors, the ventilation situations were determined to be the less-ventilated, the well-ventilated and the over-ventilated levels by comparing the actual ventilation rates with the floor’s desired ventilation rates. Therefore, the differences of indoor environments between various floors and between multi-locations on the same floor were analyzed with respect to each floor’s ventilation levels, which eventually revealed the practices of indoor environment in multistory pig buildings. The monitoring was conducted from the 11th to 21st May 2017 in Fujian province, located in southern China. Seven wireless sensor nodes were deployed on the top, ground and middle floors respectively. Each floor was monitored over 24 hours, from 9 am of the first day to the same 9 am of the next day. The results were summarized as follows: 1) Ventilation levels had a crucial impact on thermal environments. The less-ventilated levels of the 5th floor made the temperature-humidity indexes (THIs) higher than those of other floors, with an average value of 27.9 ± 0.8 close to the upper limit of comfort zone, 28.06. The radiation effects on the top floor increased the maximum temperature value of this floor to 34.5℃, 2.8℃ higher than that of the ground floor, with a highest day-night temperature difference up to 11.6℃. The temperature of the ground floor was kept in a comfortable range with a smaller day-night temperature difference due to the better thermal insulation of its floor, whereas the relative humidity was increased to a maximum of 85.7% by the moisture from the underlying surface, which was integrated to an average THI of 24.9. 2) The overall concentrations of CO2 and NH3 on each floor, under the summer ventilation conditions, were far less from the upper concentration limits. The maximum value, average value, maximum difference, and the same time maximum difference of the CO2 concentrations on the 5th floor were higher than those of other floors, contrasting with the lowest approximated CO2 emission of 1685.6 kg/d among those of three floors, which was due to its less-ventilated levels in 24 hours. The constitution of the buildings’ urinary collecting duct system influenced the NH3 concentrations dominantly, the lowest concentrations of NH3 on the ground floor benefited from the isolation of its urinary ducts from other floor’s system. 3) The difference analyses between average environmental factors of various floors and between the environmental factors of different locations on the same floor were conducted. Highly significant differences (P<0.05) were found in most environmental factors of different floors except there was no significant difference of CO2 concentrations between the 1st floor and the 7th floor. The significant differences (P<0.05) were found in some environmental factors between different locations on each floor, while no significant differences (P > 0.05) existed among other factors. Mechanically ventilated multistory pig buildings are innovative in China at present. To gain a deep understanding of animal occupant zone environments in multistory pig buildings, and further help to find design flaws of mechanical ventilation systems and disadvantages of operation strategies, the monitoring and analysis of thermal environments and harmful gases have been carried out in the multistory pig buildings during pig production, which would build up the theoretical basis and principles to improve environmental control levels of multistory pig buildings.