The trends of day/night precipitation distribution are analyzed by using the hourtohour precipitation data of 18 stations in Tibet from 1961 to 2006. The results show that the rate of night precipitation showed a decreasing trend and that of day precipitation an increasing trend in most parts of Tibet during recent 46 years; the days of night precipitation increased in winter half year in all regions, as well as in summer half year and all year in the northeastern and northwestern parts of Tibet, but decreased in the other regions; the days of seasonal and annual day precipitation increased in most parts of Tibet. The interdecadal variability of day and night rain frequency was large and has no obvious increasing trend, but had great difference between different decades in different regions.The rate of day rain was much less than normal in all year and summer half year, but greater in winter half year. The night rain days were less than normal in the eastern Tibetan and more in the central and western Tibet in summer half year. The day rain days were more than normal on the southern Tibet and North Tibet, and less in the other regions. The rate of day rain is depended on the intensity of precipitation in all year and season, but not the frequency of rains.