Abstract: Abstract: Heat stress caused by high temperature has serious adverse effect on the reproduction performance of breeding and gestation sows, so effective cooling in the sow barn is particularly important in summer. In order to improve the indoor thermal environment of breeding and gestation sows, the wet curtain cooling fan-fabric duct ventilation systems were fitted in experiment barn and their cooling effects were evaluated in this study. Cooled fresh air was delivered with fabric duct and was jetted out to sows' movement area from openings along the fabric duct to achieve local cooling. Six wet curtain cooling fans were installed on the experiment barn with 4 on the west wall and 2 on the east wall, and the fabric duct 700 mm in diameter with 1 row of Φ22 mm openings on the bottom and 2 rows of Φ26 mm openings on both lower side along the duct was matched based on airflow requirements. The fabric duct was hovered over the sow pen with bottom height of 1.5 m and jet range of 1.5 m wide. Same size barn with natural ventilation was used as control .The results showed that the daily average air temperature in the experiment and control barn were 27.7 ℃ (range from 26.4 to 29.6 ℃) and 30.2 ℃ (range from 28.4 to 32.5 ℃) (P<0.01), and the air relative humidity was 87.5 % and 82.5 % respectively (P>0.05), when the ambient average daily air temperature was 31.5 ℃ (range from 26.5 to 39.9 ℃) and the average relative humidity was 85.6%. The fan efficiency was 68.2 %. The average wind speed at the longitudinal outlets of the air duct was 7.23 m/s and was 0.99 m/s in the sows' movement areas (directly below the air duct and 0.6 m above the floor), meanwhile it was 0.16 m/s in the same area in the control barn (P<0.01). Around the air jet zone, the wind speed was higher in the center than in two sides and attenuated gradually as the height decreased. The air speed from the outlets was 7.23 m/s at height of 1.5 m and decreased to 1.20 m/s, 0.93 m/s and 0.58 m/s at heights of 1.2 m, 0.8 m and 0.4 m respectively in the jet zone. The average concentrations of CO2 and NH3 in the experiment barn were lower than in control barn (1 849 and 1.48 mg/m3 vs. 2 444 and 4.96 mg/m3, P <0.05). The daily average temperature-humidity index (THI) was 70.4 in the experiment barn and was 73.6 in control barn (P<0.01). The thermal environment based on THI was in comfort zone all day in the experiment barn, while it was in alert zone from 10:00 to 18:00 in the control barn. The average effective environmental temperature (EET) was 12.1 ℃ in the experiment barn, which means in the comfort zone all day, while the average EET was 19.5 ℃ in the control barn, which means in the range of heat stress (P<0.01). Correspondingly, the skin temperatures of sows were 33.3 and 34.1 ℃(P <0.05), and the respiratory rates were 72.3 and 87.5 beats/min in experiment and control barn, respectively (P <0.05). As for the reproduction performance of the whole pig farm, the average delivery rates from July to November were 89.3 % and 78.9 %, respectively, and the litter size were 12.6 and 11.7 heads/litter with an average litter weight of 18.0 and 17.1 kg/litter in experiment barn and control barn, respectively (P<0.05). No significant difference was found in average estrus and the gestation rate from June to September between experiment barn and no control barn (P >0.05). In conclusion, this study shows that the wet curtain fan-fabric duct ventilation system had good cooling and wind chill effect, which could effectively improve the thermal environment and relieve sows' heat stress.