Abstract: Regarding the durability issue of cement-based materials in a sulfate environment, the research focused on the anti-corrosion performance and mechanism of the cement mortar modified synergistically by graphene oxide (GO) and EVA polymer. Through long-term immersion tests in 5% and 10% Na₂SO₄ solutions, the mass loss rate, relative dynamic elastic modulus, compressive strength loss rate, and SO₄²⁻ diffusion pattern of different cement mortar specimens were tested. XRD, low-field nuclear magnetic resonance (LF-NMR), SEM/EDS were used to characterize the phase composition, pore structure and microscopic morphology of the specimens under different Na₂SO₄ concentrations and immersion times. The influence mechanism of GO and EVA on the anti-sulfate erosion performance of cement-based materials was explored at the microscopic scale. The research results showed that under the synergistic effect of GO and EVA, the mass loss rate and compressive strength loss rate at 450 d of immersion were the lowest compared to ordinary mortar, respectively, reducing by 46.2% and 51.4%, while the relative dynamic elastic modulus increased by 19.6%. The total porosity decreased by 30.9%, and the SO₄²⁻ diffusion coefficient significantly decreased. GO and EVA improved the microscopic morphology of the cement-based material, forming a multi-level synergistic protection through physical barrier and polymer film coating, effectively reducing the damage and deterioration caused by sulfate erosion, providing a theoretical basis for the design of high-performance cement-based materials for salt-affected soil environment engineering restoration.