Abstract: The paper states the results of observation and analysis of the environmental conditions of the closed floor-managed hen house at Beijing Hen Breed Farm from the summer of 1986 to the winter of 1987. The factors to be studied are room temperature, room humidity, ammonia and bacteria content in the air, room air flow velocity and room illumination intensity.After observation, the velocity and direction of air flow and the duration and intensity of illumination in the raising room are all reached the level as requyied by the physiology of hen. Unfortunately, the room temperature and the room humidity within the raising room are both too high during the summer time and on the contrary, the temperature is too low and the humidity keeps too high during the winter time in the room.The author suggests to use the wet curtain system to lower the room temperature during the summer time and to control the room temperature, room humidity and ammonia content by suitable ventilation during the winter time.