Abstract: The interface transition zone (ITZ) is the weakest part in cement-based materials and plays a decisive role in the mechanical properties and durability of cement mortar and concrete. This study explored the impact of graphene oxide coated sand (GO@sand) on the performance of cement mortar by attaching graphene oxide to the surface of sand particles. The results indicate that after stirring the sand in a GO suspension for 12 hours, the amount of GO adsorbed by the sand reaches the maximum value of 0.093 mg/g; When the dosage of GO is 0.024%, it significantly improves the mechanical and durability properties of the cement mortar, Compared to the control specimens, the 3-day compressive strength and flexural strength increase by 31.12% and 23.21%, respectively; the 28-day compressive strength and flexural strength also increase by 11.76% and 17.65%, respectively; the mortar's resistance to permeation is enhanced by 140%, and the resistance to sulfate erosion also shows a significant improvement. The analysis of the XRD and SEM test results from the hardened cement mortar specimens indicates that the GO adsorbed on the surface of the sand has accelerated the hydration process in the ITZ, increased the content of hydration products, enhanced the compactness of the ITZ, and inhibited the propagation of micro-cracks, thereby enhancing the mechanical properties and durability of the cement mortar. This paper provides a method for enhancing the performance of cement mortar using GO@sand, highlighting the effectiveness of GO@sand in ITZ nano-engineering, and indicating that this approach can be extended to other cement-based materials.