The migration characteristics of highly mobile nuclides in natural barrier are the key concerns in the long-term safety assessment of geological disposal facilities. This paper focused on typical granite in Beishan area for geological disposal of high-level radioactive waste, and established a computational model for the release and migrate of nuclides after closure of repository by GoldSim. The migration characteristics of Cs-135 and Se-79 were analyzed by Monte Carlo stochastic simulation. The results show that the migration characteristics of Cs-135 and Se-79 in intact rock are direct influ...