Liangmo developed a fresh air system for the needs of pregnant pigs. The system consists of a wet curtain air cooler, a fabric cloth duct and a special diaphragm. In the hot summer, the diaphragm is connected to the upper part of the air duct, and the cold air generated by the air cooler is sent to the pig house through the small hole at the lower end to achieve the purpose of cooling. In the winter, the diaphragm is connected to the lower part of the air duct, and the outdoor air does not pass the wet curtain of the air cooler is directly sent to the air duct cavity, and is sent from the upper end to the pig house to achieve the purpose of sending fresh air in winter.