In order to resolve the problem of imprecise and complex operations of triangular fuzzy numbers for quantitatively describing the grade of risk and importance of risk of water security system by the existing method and the problem that its aggregative risk assessment result is only real number without determining the uncertainty of the assessment result, on the basis of the indexes system of water security risk assessment according to system vulnerability concept, Monte-Carlo method was presented to simulate triangular fuzzy numbers for transforming the operations of triangular fuzzy numbers and their functions into the conventional operations of real numbers, and then an aggregative Risk based Water Security Assessment method using Stochastic Simulation and Triangular Fuzzy Numbers, named RWSA-SSTFN, was established. The application results of RWSA-SSTFN showed that the assessment of RWSA-SSTFN expressed by confidence intervals can provide more reliability information than that of common evaluation methods, which can reflect practical conditions of the aggregative risk assessment method for water security system, and that RWSA-SSTFN is intuitionistic, simple and general. RWSA-SSTFN can also be applied to comprehensive risk assessment problems of different resource and environment security systems affected by many uncertainty factors such as randomness, fuzziness and the shortage and imprecision of datum information.
