Abstract: By using linear regression analysis and Mann-Kendall test,this study statistically analyzed the climatic characteristics of hail days in 10 national stations in Ili region from 1961 to 2018,and the characteristics of the environmental field of the hail were analyzed based on the sounding data of Yining station from 2000 to 2018.The results showed that:（1） There was a big difference in the spatial and temporal distribution of hail days in Ili area,and as the altitude increased,the number of hail days also increased rapidly.The annual number of hail days showed a downward trend in general,with a linear tendency rate of-0.413 time·a-1.The seasonality of hail was remarkable.The earliest hail of the year occurred in March,and the latest was at the beginning of November.From May to July,it was the period of the high occurrence of hail,the daily hail was mainly concentrated at 16:00-20:00.According to result of the Mann-Kendall test method,the number of hail days began to decreased in1981,and the turning point appeared in 1999,after which the number of hail days decreased significantly.（2） The temperature and humidity profile of most of the process T-ln P diagrams were of dry adiabatic type,that was,the entire layer had low humidity and the dew-point deficit was greater than 5 ℃.Meanwhile,the thresholds of key environmental parameters before hail occurred in each month were summarized.