Abstarct: In general, various methods are used for tunnel construction. Therefore, estimating the construction duration is of great importance in the feasibility and initiation stages of the project. Conventional tunnel scheduling and estimation methods are often traditional and do not provide accurate estimates. In this study, the effective criteria for the construction duration of long tunnels, especially those excavated by mechanized methods, were identified. Then, they were ranked using the developed fuzzy hierarchical analysis method. Thus, the impact and importance of each of the effective risks on operations were determined. In this study, the risks affecting the scheduling of long tunnel construction were divided into two groups: known and unknown risks. Then, by designing a questionnaire and using expert opinions, each of the existing criteria were scored. Then, the improved fuzzy hierarchical analysis method (Bucly's geometric mean method) was used to rank and weight the criteria and sub-criteria that caused an increase in the actual tunnel scheduling. In the next step, using fuzzy hybrid methods, the criteria that had a greater impact on known and unknown risks were selected as input parameters for the Monte Carlo simulation method, and then the impact of these risks on tunnel scheduling was determined using the Monte Carlo method in MATLAB software. In the presence of known project risks, there is a 100% probability that the project will be completed on schedule in the first year. In the second year, scheduling decreases and there is an 89% chance of completing the project on schedule. Similarly, in the third year, 92%, in the fourth year, 90%, in the fifth year 90%, and in the sixth year also 90% of the project is expected to be completed on schedule. In the presence of unknown project risks, there is a 90% probability that the project will be completed on schedule in the first year. In the second year, scheduling increases and there is a 92% chance of completing the project on schedule. Similarly, in the third year, 93%, in the fourth year, 90%, in the fifth year 92%, and in the sixth year also 92% of the project is expected to be completed on schedule. Finally, the results were compared and reserves under the tixtles of contingency reserves and management reserves were presented as solutions to deal with these risks. Therefore, the necessary predictions should be made before starting tunneling projects for these issues in order to minimize the delay in project scheduling.