Abstract: Graphene oxide (GO) and carbon nanotubes (CNTs), as nanomaterials with abundant chemical activity and excellent mechanical properties, exhibit great potential in improving the performance of cement based materials. However, most existing studies have focused on single doping systems, and the synergistic reinforcement mechanism of GO/CNTs composites and their interaction behavior within cement matrices have not been thoroughly investigated. Based on this, GO/CNTs composites with different ratios were incorporated into cement mortars with three water-cement ratios to investigate the variations in their mechanical properties at 7 and 28 days of curing, and the crack propagation patterns were observed using digital image correlation (DIC) technology. The results show that at a water-cement ratio of 0.4 and an age of 28 days, the composite group 4G2C exhibited the highest compressive strength of 51.09 MPa, which was 39.25% higher than that of the control group. Under the same water-cement ratio, the compressive strength values of all composite groups were higher than those of the single doped GO and CNTs groups. The DIC strain field indicated that the incorporation of GO and CNTs caused crack deflection and branching, significantly enhancing the toughness of the cement mortar. Microstructural analysis further confirmed that the GO/CNTs composite promoted the hydration reaction, optimized the matrix pore structure, and inhibited the initiation and propagation of microcracks, thereby achieving synergistic reinforcement from the nanoscale to the macroscale. The findings provide a theoretical basis for the application of nanocomposites in high-performance cement based materials.