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.