In this study, the spatial changes of precipitation in the Great Karun basin were discussed and investigated using the Shannon entropy method. In order to further investigate the changes of precipitation in the basin, the correlation between the entropy value and the annual precipitation for each station was calculated and evaluated. The results showed that the highest amount of entropy occurred in the southwestern areas of the basin in the studied months, while the northern and especially the northwestern areas of the basin showed the lowest amount of entropy. Since the amount of entropy is directly related to rainfall irregularity, rainfall irregularity is greater in the southern regions of the basin than in the northern half of the basin. In other words, in the northern areas of the basin, precipitation occurred regularly during the years under study, while in the southern areas of the basin, less regularity and continuity are observed. However, based on the spatial distribution of entropy in January and February, it can be said that precipitation is not an unexpected phenomenon in all regions. Monthly correlation analysis of entropy with annual cumulative precipitation shows that the months of November to February are crucial in creating wet or dry yearly conditions in the southeast and east of the basin. In this respect, February is more important for the west of Khuzestan province. More result show that the annual precipitation anomaly in the northern half of the basin is related to the precipitation in March. April rainfall does not play a role in the annual rainfall anomalies of Khuzestan Province, but is a determining factor in most other parts of the basin.