Abstract: Multi-floor pig building has been widely used to save the land use of farms in large-scale production in recent years. Fresh air filters and exhaust deodorization walls can be often added to reduce the odor emission for a better biosafety level. This study aims to evaluate the air quality in the environment of the barn in the multi-floor pig building equipped with a fresh air filter and exhaust deodorization wall in summer. The experiment was performed on a multi-floor pig building in the suburbs of Beijing, China. The ground (1st floor), middle (3rd floor), and top (5th floor) floors were selected as the experimental objects, each of which Unit 3 was as the experimental barns. All barns were equipped with a fresh air filter and an exhaust deodorization wall. The cleanliness levels of the fresh air filter device were clean, poorly clean, and relatively clean on the ground, middle, and top floor, respectively. A continuous measurement was made on the static pressure difference at the fan, temperature, relative humidity, and carbon dioxide concentration of the barn on different floors. At the same time, the temperature and humidity index (THI) and the maximum temperature difference were calculated to compare the temperature distribution and environmental comfort of the barn on different floors. The results showed as follows. The static pressure differences at the fan on the ground, middle and top floors were 69.7, 110.1, and 98.7 Pa, respectively. Moreover, the ventilation volumes of a single fan on the ground, middle, and top floors were 49 580, 34 219, and 38 935 m3/h, respectively. Since six fans were turned on both the middle and top floor, the real ventilation volume and fan energy efficiency ratio of the barn were significantly lower than those on the ground floor, where five fans were turned on (P<0.05). The numbers of gilts on the barn for the ground, middle, and top floor were 420, 570, and 550, respectively, while, the corresponding real ventilation rates were calculated to be 590, 360, and 425 m3/h, respectively. The environmental parameters on the ground floor, such as the temperature (24.2 ℃), and the maximum temperature difference at the same time (0.4±0.1) ℃, were significantly lower than those of other floors (P<0.05). The maximum temperature difference at the same time on the middle floor (1.1±0.4) ℃ was significantly higher than those on other floors. The maximum temperature difference at the same time on the top floor (0.6±0.2) ℃ was significantly lower than on the middle floor, however, the ambient temperature at the front and rear was significantly higher than those on other floors. The Equivalent Temperature Index for Sows (ETIS) of the ground floor (28.9) was significantly lower than those of other floors. In conclusion, the poor cleanliness of the fresh air filter device contributed to an increase in the static pressure difference at the fan, which in turn caused the real ventilation volume of the pig barn and the energy efficiency ratio of the fan to decrease. The ground floor presented the best cooling effect and thermal environment uniformity in summer, particularly with the decrease of the ventilation, where the ETIS gradually increased for the barn. The finding can also provide a theoretical basis to improve the ventilation efficiency and the breeding environment of multi-floor pig buildings in summer.