In order to develop a clay-based cementitious material used in hydraulic engineering, the waste clay from a waterway revetment was used as a raw material. The influence of different contents of inorganic binder, such as cement, gypsum, and slag, on the mechanical properties of the clay-based cementitious material was studied by testing the compressive strength, splitting tensile strength, and water stability of specimens. A scanning electron microscope(SEM)was used to analyze the microstructure of specimens. The results show that when the mixing proportions of the waste clay, cement, slag, gypsum, and lime are 65%, 18%, 10%, 2%, and 5%, respectively, the compressive strength, immersion strength, and splitting tensile strength of the clay-based cementitious material at 28 d reach 25.6 MPa, 24.1 MPa, and 2.5 MPa, respectively. SEM results show that cement-based cementitious materials, such as C-S-H, were observed at different hydration ages, and these products effectively improve the mechanical properties of the clay-based cementitious material. It is concluded that the clay-based cementitious material shows high strength and water stability, and it can be used in hydraulic engineering.