In the tunnel lining structure internal force calculation

it is indeterminacy for mechanics parameters of surrounding rock and parameters of structure. At the same time

the indeterminacy has the boundary

which can be estimated by a reasonable interval numbers in engineering. Changing a single random variable in the interval numbers

the structural internal force can be solved by adopting a finite element equation. But in the case of multi-variable

considering indeterminacy of calculation model and complexity of mathematical solution

the finite element procedure can be used to educe the action effect of each variable to structure’s internal force

then the interval values consist of different parameters are obtained; and the interval values of tunnel lining structural inner force are confirmed finally. The method can provide a new method for the calculation of interval numbers of tunnel lining and engineering application.