The purpose of this study was to evaluate the environmental risks of Alborz Dam on Bababrood River in Babol city, using multi-criteria decision making methods. Initially, environmental identification of the study area was carried out, Then a list of environmental risks identified in the construction and exploitation phase was prepared and presented to environmental experts familiar with the Alborz dam area in the form of a questionnaire. environmental risks scored by environmental experts based on three indicators, Severity of occurrence, Probability of occurrence, Then environmental risks ranking was performed using TOPSIS and Fuzzy TOPSIS methods. The most important risks of Alborz dam using TOPSIS method in the construction phase, respectively: Was Obtained, Destruction of forest within the dam with a score of 0. 926, Displacement of reservoir residents with a score of 0. 837 And in the phase of operation: Thermal stratification of dam reservoir with a score of 0. 847, Landslide with a score of 0. 751. Also, the most important risks of the Alborz dam using the Fuzzy Topsis method in the construction phase, respectively: Was Obtained, Displacement of reservoir residents with a score of 0. 682, Demolition of forest within the dam with a score of 0. 677, And in the phase of operation, respectively: Thermal stratification of dam reservoir with a score of 0. 645, Landslide with a score of 0. 630. Finally, one method of integration (average rating method) was used to resolve the conflict between the results.