The invention discloses a preparing method for a copper-indium-gallium-selenium alloy. The preparing method includes the steps that raw materials of copper, indium and gallium are selected according to weight parts, broken into coarse powder and are mixed evenly; airflow grinding is conducted; the mixed powder obtained after airflow grinding is loaded into a reaction kettle, and argon is charged into the reaction kettle after vacuum pumping is conducted; the temperature of the reaction kettle is increased to 300 DEG C to 400 DEG C; the temperature of the reaction kettle is increased to 600 DEG C to 800 DEG C; the temperature of the reaction kettle is increased to 900 DEG C to 1100 DEG C; the reaction kettle is cooled to 80 DEG C to 100 DEG C, and a copper-indium-gallium alloy is obtained; the copper-indium-gallium alloy and selenium powder are loaded to the two ends of a quarts tube correspondingly, and vacuum pumping operation is conducted on the quarts tube; a tubular furnace is adopted for heating one end of the copper-indium-gallium alloy to 1050 DEG C to 1100 DEG C, and the temperature is kept; the end provided with the selenium powder is heated while the end provided with the copper-indium-gallium alloy is heated by the tubular furnace; copper, indium, gallium and selenium are reacted for 20 h to 30 h under the temperature of 800 DEG C; and the tubular furnace is closed, heating is stopped, cooling is conducted to the room temperature, and the copper-indium-gallium-selenium alloy is obtained. By means of the preparing method, the reaction time is shortened, and industrial production is facilitated.