Drought, as the most important natural hazard, causes economic, social, environmental, social and security losses in large areas of the planet every year. Undoubtedly, the first step in dealing with drought and its consequences is the accurate recognition and understanding of this phenomenon and its effects in all dimensions. To achieve this purpose; In the present research, the severe and widespread droughts of Iran's watersheds in the last 30 years, were investigated using the daily rainfall data of the synoptic and climatology stations of the country with at least 30 years of statistics. Standard precipitation index was also used to determine the severity of drought in Iran. The evidence indicates that currently, most regions of Iran are experiencing severe and very severe droughts. The share of terrible in the country is very small and only the northern half of Iran in the watershed of the Mazandaran Sea and its southern shores in the vicinity of permanent forests and rivers, as well as the mountainous junction of the north-west of the country in the watershed of the Urmia lake, in its southern neighborhood with many dams and rivers, has a small amount of protection. Also, the trend of long-term changes in rainfall and drought shows that the annual rainfall in Iran is decreasing with a rate of 1.17 mm per year and all types of drought in the country have recorded an increasing trend. In general, it can be said that the drought in Iran has both intensified and spread and it is not limited to hot and dry interior regions and has even penetrated in the northern, northwestern and western half of Iran. Besides, the deserts in Iran are very few, concentrated and follow the phenomenon of climatic implantation.