Stochastic simulation method considering the heterogeneity of hydraulic conductivity is suggested in this paper. Hydraulic field is simulated by using our FEM code for THM coupling processes. The results show that hydraulic gradient at different location around the cavern is differently dependent on water-curtain pressure in deterministic model. A probability range of hydraulic gradient at each point with 10m space between each was examined by means of stochastic realization of spacial variability of hydraulic conductivity. These analyses are contributed to determine the values interval of water-pressure and groundwater flux into the cavern with a given security for LPG containment design and evaluation considering the spacial variability of hydraulic conductivity.