Based on measured data from 1961 to 2017 in 18 national weather stations in Ganzi Tibetan Autonomous Prefecture, the monthly, seasonal and annual wetness index for Ganzi and its affiliated counties were counted according to the method described in Ecological quality Assessment Criteria of Meteorology.The spatial and temporal evolution characteristics of climate dry and wet were also analyzed in this study, which will provide scientific basis for drought prevention and mitigation and rational utilization of climate resources. The results showed: (1) the average wetness index of Ganzi in the past 57 years was between 0.67-1.33, the highest value was in 1965, and the lowest was in 1973. The seasonal average wetness index was between 0.07-1.86, the highest value occurred in summer, the second highest value occurred in autumn, and the lowest value occurred in winter; (2) The average wetness index of counties (cities) in Ganzi was between 0.23 and 1.73, which presented a large difference between the various regions.It seemed that the southeast and north was relatively humid and the southwest was relatively dry; (3) The annual climate change rate in Ganzi was 13.4mm·10y~(-1), the climatic tendency rate of the wetness index was-0.003·10y~(-1), and the climate tends to be weakly warm and dry. (4) The average wetness index of 2/3 counties (cities) in Ganzi was less than 1, which indicated that the seasonal drought characteristics was significant, and the ecological environment was fragile. Production practices should follow the principle of the combination of exploitation and protection. The drought prevention and mitigation, farmland water conservancy construction, and ecological restoration also should be strengthened during the production process.