Abstract: The floatability of chalcopyrite and molybdenite is similar, and it is often necessary to add a depressant to achieve efficient separation of copper and molybdenum. However, there are many problems with traditional chalcopyrite depressants, such as low selectivity, low efficiency, and environmental pollution. Therefore, it is necessary to develop a new and efficient chalcopyrite depressant. The effect of the self−made inorganic depressant GX1 on the flotation behavior of chalcopyrite and molybdenite was studied by single mineral and artificial mixed ores flotation. The contact angle, Zeta potential, infrared spectroscopy, and X-ray photoelectron spectroscopy were used to analyze the interaction mechanism between GX1 and minerals. The flotation experiments showed that GX1 significantly increased the floatability difference between chalcopyrite and molybdenite. Under the conditions of MIBC 10 mg/L, GX1 300 mg/L, pH = 10, and kerosene 20 mg/L for the artificial mixed ore, the recoveries of chalcopyrite and molybdenite were 17.25% and 90%, respectively, with the difference of 72.75%. Control experiments further confirmed that the depressant effect of GX1 on chalcopyrite was superior to that of sodium sulfide. The contact angle tests showed that the contact angle of chalcopyrite decreased from 65° to 20° after treatment with GX1, while the contact angle of molybdenite decreased only slightly, from 88° to 74°. Additionally, the Zeta potential of chalcopyrite surfaces treated with GX1 shifted significantly towards the negative, whereas the Zeta potential of molybdenite showed little change. FTIR analysis results indicated that new absorption peaks and chemical bonds formed when GX1 adsorbed on the chalcopyrite surface, while molybdenite did not show any new absorption peaks after GX1 treatment. The binding energy changes observed in the XPS tests suggested that GX1 readily interacted with Cu and Fe on the chalcopyrite surface, altering its floatability, whereas the physical adsorption of GX1 on molybdenite had no effect on its floatability. This selective separation achieved copper-molybdenum separation.