Abstract: The artical takes water transporting from oceans through atmosphere to the continents as a key link of water circulation, which consists of evaporation, precipitation, atmospherical circulation and runoff as its main constituents, related closely with climate and its change. From the main zone of evaporation in oceans, the summer monsoon is the essential current of water transportation. The high variability of monsoons would cause the high variability of water cycling. The artical discusses how El-Nino and global warming influences the water cycling and precipitation. It is highlighted that the importance of human activities is one of the causes forming the water deficiency in modern times and confirms that man would be able to reestablish the harmony between nature and man, and successfully solves the water problems confronted.