Abstract: According to the principle that water vapor condenses and the latent heat is released when the hot-humid air encounters the surface of low-temperature solid object and making use of the environmental conditions such as high air temperature, high air humidity, low soil temperature inside the plastic covered tunnel greenhouse in sunny winter, a set of air-circulating and regenerative dehumidification device was designed and installed. By which, the hot-humid air of top-mandatory level was transported into the various underground channels by axial fan, and was exhausted from another exit. Thus the indoor air cycle was formed getting to the aim of dehumidification without the temperature drop. The observation results showed that compared with the control plastic greenhouse, air relative humidity at the height of 1.7 meters inside the experimental plastic greenhouse decreased apparently, reaching a significant level (P＜0.05) or a greatly significant level (P＜0.01) within most periods in January. At all punctual moments in the sunshine, the mean values of air temperatures at the height of 1.7 meters and the soil temperatures at the depth of 20 cm inside the experimental plastic greenhouse were higher than those inside the control plastic greenhouse, over 0.1～3.0℃, 1.4～1.7℃ respectively.