In this paper the climatic effects of waters in different natural conditions are studied according to the theoretical analysis and the observational results of twenty six waters located in various regions in China, the main conclusions are as follows: 1. Deep water has temperature increasing effect in winter and temperature decreasing effect in summer. Shallow water has temperature increasing effect all the year in general, but has temperature decreasing effect in summer in arid regions. 2. In arid regions, the misture of air over water is obviously greater than that over land. In humid regions, the air moisture above waters is generally higher than that above land, but in the rice area the mean relative humidity in all seasons and the mean vapour pressure in summer above water are probably lower than that above rice field. 3. The wind velocity at the height of 2m above water may increase by 20%～100% compared to that over land. On an average it may increase by 50%. The weaker the wind, the larger the increased percentage of the wind speed over water. 4. In the Chinese monsoon region, in general, the summer and annual precipitations in water area and off shore decrease obviously, and the winter precipitation increases somewhat, while it is exactly the reverse at the sites which are far away from waters. In the arid region, however, the precipitations on water and its neighboring area increase all the year. 5. The climatic effects of waters is more obvious when the waters are larger and deeper and the climate is dry.