This study aimed to analyze the relationship between the phases of the ENSO phenomenon and the 30-year autumn precipitation in Kermanshah province using the ONI index. Autumn precipitation plays an important role in providing water resources and agricultural management in Kermanshah province, and its changes under the influence of atmospheric fluctuations such as ENSO can have significant economic and social consequences. Two sets of data were used, including monthly data from the Kermanshah synoptic station and seasonal data from the ONI index received from the NOAA website for 1994-2023. Pearson correlation coefficient was used to determine the relationship, and based on the phase detection criterion, the El Nino and La Nino phases were separated and the different intensities of both El Nino and La Nino phases were extracted and examined. The relationship between precipitation in the study area and the aforementioned distance index in the autumn season is direct, which was significant at the 99% confidence level (R=0.51 and P<0.01). The average precipitation in the moderate El Niño phase has dominated the other intensities of this phase, and the average precipitation in the mild El Niño phase has been higher than the other levels of this phase. The lowest precipitation at the mentioned station during the study period was at the average level of the El Niño phase with a value of 23.33 mm, and the highest precipitation in the 30-year period was at the average level of the El Niño phase with a value of 427.88 mm.