In this study, in order to solve problem that graphene (G) is easy to agglomerate in cement paste, the co-addition of hydroxyl graphene (HO-G) with better dispersion and graphene was adopted to improve the agglomeration phenomenon of graphene. The effect of co-addition of graphene and HO-G in different mass ratios on mechanical properties and durability of cement mortar was studied. The microscopic tests MIP, SEM and XRD were carried out on mortar specimens after 28 d of curing. The results show that the co-addition of graphene and HO-G in different mass ratios exhibits a more significant strengthening and toughening effect and improves the durability of cement mortar at the same time, but has little impact on the workability of cement mortar. When the mass ratio of co-addition of graphene and HO-G is 3∶7, the mechanical properties of cement mortar are the best. Compared with reference group, the 28 d flexural strength and compressive strength improve by 11.1% and 26.2%, respectively. The co-addition of graphene and HO-G in cement mortar refines the internal pores of mortar, and regulates the growth of cement hydration products, resulting in a more regular and dense internal structure of cement stone, which enhance the durability of cement mortar specimens.