Abstract: The spatial-temporal variation of rainfall in the Jinsha River basin is investigated by using monthly precipitation data collected from twenty-eight meteorological stations between 1971 and 2011. Voronoi method which is based on ArcGIS platform is applied to calculate average annual and seasonal precipitation. Spatial interpolation method of inverse distance weighting, also based on ArcGIS platform, is utilized to analyze the spatial variation in precipitation and its variation trend. Linear regression method, moving average method, Kendall ranking test and precipitation concentration index are used to analyze variation trend in annual and seasonal precipitation and its distribution throughout the year. The mutation of precipitation is studied by Mann-Kandall rank statistic method and the periodical changes in precipitation are analyzed by Morlet wavelet. The results show that the spatial distribution of precipitation was uneven. The precipitation of annual, spring, summer and winter showed an increasing trend, except for the autumn; its distribution followed a seasonal variation. The sudden change in the precipitation of spring, summer and autumn occurred in 1999, 1979 and 2001 respectively; there was an annual and seasonal precipitation cycle of 5 to 22 years.