Abstract: In the near field environment, the migration and diffusion of radionuclides in the buffer material is controlled by the coupling effect of temperature field, seepage field, expansion stress field and chemical adsorption field. The blocking characteristics of the buffer material will affect the ability of the radionuclides to return to the biosphere with the migration of groundwater to the surrounding rock of the disposal reservoir. It is of great significance for long-term safety assessment of geological disposal repository to study the long-term retarding effect of buffer material on nuclide uranium under the coupling effect of multiple factors. Based on mixture theory, continuum theory, mass conservation, momentum conservation, energy conservation and solute diffusion of Fick’s law, thermal-hydro-mechanical-chemical coupling control equation of nuclide migration and diffusion in saturated buffer materials was constructed. At the same time, with the help of the direct full coupling solution advantages of COMSOL Multiphysics software, using the self-developed Mock-up experimental device for long-term retarding performance of buffer materials as a geometric model, the direct coupling analysis of the migration and diffusion behavior of uranium in saturated buffer materials under the action of multiple physical field coupling is realized by using the built-in interface and the coupling term in THM coupling control equation as the source term. The numerical simulation results of long-term retardation characteristics show that the migration and diffusion of uranium in the buffer material is slow at the initial stage, and the migration distance increases by about 1 m with time. However, in the middle and late stage, as the adsorption capacity of buffer material for uranium tends to be saturated, the migration distance increases more obviously than that in the early stage, and the migration distance increases by about 3 m with time. The method of constructing and solving thermal-hydro-mechanical-chemical coupling control equation for the migration and diffusion of nuclides in saturated buffer materials under multi-factor coupling and simulating the long-term retarding performance can provide technical reference for the 1∶1 engineering barrier design and safety performance evaluation of underground laboratories of deep geological disposal repository for high-level radioactive waste  in China.