Abstract: To reveal the mechanism of ultrasonic pretreatment of calcium oxide to improve the flotation effect of chalcopyrite, the flotation of chalcopyrite was carried out with ultrasonic pretreatment of calcium oxide as the regulator. The ultrasonic pretreated calcium oxide solution was characterized by FTIR. The results revealed that the calcium oxide solution suitable for ultrasonic power treatment had obvious influence on the efficiency of chalcopyrite flotation. After 500 g/t calcium oxide was treated by ultrasonic wave with 216 W output power, the recovery of copper in concentrate reached 83.23%, which was 9.48% higher than that without treatment. Appropriate ultrasonic treatment of calcium oxide solution could increase the content of Ca²⁺, Ca(OH)⁺ and OH^-, and the Ca²⁺ and Ca(OH)⁺ plasma could reduce the consumption of flotation agent. In addition, the appropriate ultrasonic power pretreatment could also increase the content of hydroxyl group in free water in calcium oxide solution which was conducive to the flotation of chalcopyrite by 3.13%, so as to improve the flotation effect of chalcopyrite. The research provides a reference for the application of ultrasonic technology in flotation field.