Phosphate cementitious materials have good mechanical properties, and simple preparation process, which provide a new way for resource utilization of copper slag. Phosphate cementitious materials were prepared using copper slag and sodium dihydrogen phosphate (NaH2PO4) as raw materials. And the effects of raw material mix ratio and curing conditions on compressive strength, phase and microstructure of copper slag-based phosphate cementitious materials were studied by universal testing machine, X-ray powder diffractometer and scanning electron microscope. Besides, the thermal stability of copper slag-based phosphate cementitious materials was also investigated by simultaneous thermal analyzer. The results show that raw material mix ratio has an important influence on mechanical properties and microstructure of phosphate cementitious materials. And appropriately increasing the curing temperature is conducive to strength development. When the mass ratio of NaH2PO4 to copper slag is 0.30, the mass ratio of water to NaH2PO4 and copper slag is 0.15, and the curing temperature is 60 ℃, the 7 d compressive strength of copper slag-based phosphate cementitious materials is as high as 54.70 MPa. The excellent mechanical properties are due to the dense amorphous phase formed by the reaction of fayalite (Fe2SiO4) in copper slag with NaH2PO4. Furthermore, the copper slag-based phosphate cementitious materials have good thermal stability. It begins to be oxidized and decomposed at 467 ℃ under air atmosphere, and the amorphous structure phase undergoes phase transition.