Based on the investigation of the microclimate in some cases in western Guizhou Province, the author projposes that the wind speed in a cave depends on the number of mouths of the cave and the shape of it. The air temperature in a cave is determined by the thermal character of groundwater or rock and by the air movement .in it. The humidity in a cave is related not only with the wind in the cave and the shape of the cave, but also with the volume of groundwater the flows into the cave. Normally, the relative Humidity is 90-.100%, expect for the mouth's area of the cave through which wind is blowing.