The chloride penetration resistance， sulphate erosion resistance and water absorption were used to investigate the effect of single addition of ethylene-vinyl acetate copolymer powder（VAE） and composite addition of VAE/ nano SiO₂（NS） on durability of cement-based materials. Attempt was made to explore the influence mechanism of single addition of VAE and composite addition of VAE/NS on the durability of cement-based materials by means of X-ray diffractometer， thermal analyzer， scanning electronic microscope， mercury porosimeter and Fourier transform infrared spectrometer. The results show that both single addition of VAE and composite addition of VAE/NS can improve the chloride penetration resistance and sulfate resistance， and decrease the total water absorption， and the effect of composite addition is better than that of single addition. The single addition of VAE improves the hydration properties， and reduces the harmful and multi-harmful pores by 65.3%， but increases the most probable aperture and the n（Ca）/n（Si） value of interface transition zone. The composite addition of VAE/NS further improves the hydration properties， reduces the harmful and multi-harmful pores by 82.6%， significantly increases the amount of hydrate calcium silicate（C-S-H） generation and the degree of polymerization， and thus enhances the durability of cement-based materials.