More than 8 000 grottoes and cliff statues are located in Sichuan and Chongqing. Most are made from sandstone. The sandstone has deteriorated due to long-term environmental effects, posing a threat to the cultural relics. Graphene sheets are added to the traditional mortar of the sandstone cultural relics to enhance the properties, which is defined as “CH@G mortar”. The mechanical properties and volume stability of the CH@G mortar are enhanced by the graphene sheets. The highest strength is obtained by the addition of 0.07% graphene sheets, and its values (increased proportion compared with CH mortar) of compressive strength, flexural strength and tensile strength at 56 d are 4.21 MPa (7.36 %), 2.21 MPa (19.46%) and 0.47 MPa (51.61%), respectively. The FT-IR and Raman spectra results show that the graphene sheets have little influence on the composition of the products, and could accelerate the hydration in the early days, according to the XRD results. The SEM images show that graphene sheets could form a uniform and compacted microstructure.