Abstract: The temporal and spatial distribution of the Tian Shan mountains (TM) area precipitation, water vapor transport, the precipitation conversion rate from outer water vapor, the atmospheric moisture cycle and possible causes for the precipitation conversion rate anomaly over the TM was investigated by using monthly precipitation data from 79 observation stations in and around the TM and the NCEP/NCAR reanalysis daily dataset with 1°(latitude)×1°(longitude) horizontal resolution during 2000-2010. Results from the analysis show that: 1) The average precipitation is above 450 mm in the western and middle areas of the TM, but only about 150 mm in the eastern and southwesterly areas of TM. The total area precipitation in the spring, summer, autumn, and winter is 291.4, 625.9, 218.1, and 73.6×10⁸ m³, respectively, which, when converted to mm precipitation, is 108.2, 232.4, 81.0, and 27.4 mm. Annual precipitation is 449.0 mm. 2) The monthly water vapor transport shows a single-peak normal distribution, with a July maximum and a January minimum. Water vapor transport for spring, summer, autumn, and winter is 24.5%, 41.3%, 22.3%, and 11.9%, respectively. 3) The precipitation conversion rate for spring, summer, autumn, winter, and for one complete year is 10.3%, 12.6%, 8.5%, 5.4%, and 9.2%, respectively. The precipitation conversion rate is strongly related to the position and strength of the Iran high, Lake Baikal ridge, and the West Asia subtropical westerly jet stream, but is unrelated to water vapor input.