Abstract: Aiming at the problem of insufficient use of geological prospecting data in the traditional random field simulation of spatial variability of surrounding rock parameters, the constraint random field generation method based on sampling data is developed through the combination of the Karhunen-Loève series expansion method with the Kriging interpolation. Besides, combined with Monte Carlo simulation, non-intrusive stochastic finite difference analysis and stratigraphic structure model, the optimization analysis model of spatial variability of surrounding rock parameters based on constrained random field theory has been realized. This model is used for reliability analysis of the mechanical response of surrounding rocks during the construction of Hejie Tunnel. The results show that through the constraint of the surrounding rock mechanical parameters at specified location, the optimization model can introduce the known information into the reliability analysis as much as possible, reduce the discreteness from the actual condition and improve the calculation precision of reliability analysis.