中文摘要：

针对未确知数学处理湖泊水库水环境系统众多不确定性信息中对未确知变量数、可能值区间分段数及采用的运算算子要求较高限制了未确知数学理论广泛应用的问题，提出肘蒙特卡罗法模拟未确知数的可信度分布，根据满足可信度分布的未确知数试验值可直接进行未确知数运算。湖库水环境容量计算实例结果表明，该方案可行有效，计算结果可靠，对未确知数学在各学科领域广泛应用具有一定的推动价值。

英文摘要：

Unascertained mathematics theory is an useful tool to deal with the uncertainty of unascertained information in the lake and reservoir water environmental systems. However, the widely applications of unascertained mathematics are limited due to the problems, such as the number of unaseertained variables, subsection of faith degree and the operators which are used in the operation. Hence, a Monte Carlo-based operation scheme was presented to solve these problems. The faith degree of unascertained variables can be simulated by Monte-Carlo methods, and calculation results can be directly obtained by the operation of trial values through traditional arithmetic operators. Results of case study of the water environmental capacity （WEC） calculation in lake and reservoir indicate that the simulated cumulative faith degree function of WEC by Monte Carlo simulation behaves very well. It also shows that Monte-Carlo based unascertained number operation scheme is feasible and reasonable, which will bring a widely application of unascertained mathematics theory.