Abstract: The uncertainty for determination of molybdenum content in molybdenum iron (MoFe60) by gravimetric method was evaluated based on Monte Carlo method. The corresponding mathematical model was established based on GB/T 5059.1-2014, and a correction factor representing the random effect was introduced. The probability distribution function of the input quantity was set by the experimental data. Then the Monte Carlo random sampling was realized with MCM Alchimia^® 3.0. The simulated results of Monte Carlo method was (59.98 ±0.20)%, k=2, which was consistent with that of the GUM method. The Monte Carlo method could be used to evalute the uncertainty of gravimetric method.