Abstract: In order to find the environment distribution in enclosed layer housing in winter, some research work was done in Beijing region. Temperature diference between inside and outside could be about 19℃, the CO_２ consistence was about 2 100×10^－６, the NH₃ consistence was no more than 18×10^－６ when the ventilation rate is 1.3m³/h for each layer. The forms and locations of air inlets affect obviously the distribution of inside temperature and harmful air components.