为解决JC法计算隧道衬砌可靠指标过程中极限状态选用方法的缺陷，通过随机有限元方法和Monte-Carlo法对时速350 km高速铁路双线隧道Ⅲa、Ⅳb型衬砌进行抽样计算，得到2种衬砌各截面偏心距平均值和变异系数； 通过对素混凝土和钢筋混凝土衬砌极限状态功能函数及其适用条件的分析，引入几何优化法，以约束函数表示功能函数的约束条件，建立可靠指标的优化求解模型； 选用寻优性能良好的Global Search函数，对2种衬砌各截面可靠指标进行优化求解，并与JC法进行对比，证明优化方法的优势。

In order to solve the defects of selecting method of limit state in the process of calculating reliability indices (RI) of tunnel lining by JC method, the random finite element method and MonteCarlo method are used to sample and calculate the type Ⅲa and Ⅳb linings of 350 km/h highspeed doubletrack railway tunnel. The mean value and coefficient of variation of eccentricity of two kinds of lining sections are obtained. And then the ultimate state function and applicable conditions of plain concrete and reinforced concrete lining are analyzed; the geometric optimization method is introduced to represent the constraint conditions of ultimate state function and establish the optimization model of RI. Finally, the Global Search function with good optimization performance is used to optimize the RI of two kinds of lining sections, and also it is compared with JC method to prove the advantages of the optimization method.