There are a number of uncertainties in estimating reservoir sedimentation and accumulation which are related to amount of streamflow, sediment load, sediment particle size, specific weight, trap efficiency and reservoir operation. In this study, to analyze the uncertainty of annual reservoir sedimentation, the accumulated reservoir sedimentation data for 46 years has been used and an empirical model to estimate the volume of reservoir sedimentation based on Fuzzy α-cut method has been developed in MATLAB software environment. Two fuzzy membership function with five level of α-cut have been used to calculate the uncertainty annual reservoir sedimentation, trap efficiency and accumulated reservoir sedimentation. The calculated uncertainty is about 0.641, 0.023, 0.344, respectively. The results have shown that the streamflow has an important role in uncertainty, i.e. uncertainty increases while the streamflow is increased. Sediment load factor and the trap efficiency have the most and least effects on uncertainty of Latian reservoir sedimentation volume estimate, respectively.