Abstract: Buffer material was the last artificial barrier of high-level radioactive waste repository, and its retardation capability to radioactive nuclides would directly affect the security and stability of the repository system. Bentonite was a suitable mineral, which can be used to build an integrated buffer material because of low hydraulic conductivity, good swelling and sealing properties, plasticity and high sorption capacity. Bentonite-zeolite-pyrite type integrated buffer material was constituted by the bentonite-zeolite-pyrite weight ratio was 63∶27∶10 (abbreviated as B₇ZP), that zeolite and pyrite were chosen as mineral additives. Then constant source diffusion experiment was carried out to investigate strontium diffusibility in B₇ZP with initial dry density of 1.70 g/cm³. The experimental results indicate that B₇ZP has good retardation capability for strontium, and the apparent diffusion coefficient of strontium is 3.3×10^-12 m²/s, smaller in B₇ZP than in pure bentonite. The convection-diffusion-adsorption multi field coupling model for strontium migration was established based on the theory of porous media pollutant migration. MATLAB software was used to analyze migration distance of strontium in B₇ZP under the condition of different time scales, seepage velocity, apparent diffusion coefficient and retardation factor. These research results can supply reference for usage of barrier materials and assessment of long-term retardation capability.