The invention discloses a tube-expanding device of an air-condition heat exchanger, comprising an expanding head and an expanding rod. One end of the expanding head is arranged at the end part of the expanding rod and can rotate along an axial line of the expanding rod, and the surface of the expanding head is provided with teeth lines matched with the shapes of screw thread teeth inside a copper tube of the heat exchanger. Compared with the prior art, the tube-expanding device of the air-condition heat exchanger has the advantages that because the surface of the expanding head is provided with the teeth lines matched with the shapes of screw thread teeth inside the copper tube of the heat exchanger, the teeth lines of the expanding head are embedded in the screw thread teeth inside the copper tube when the copper tube of the heat exchanger is expanded, and the expanding head can rotate along with the screw thread teeth when expanding the tube, the tube-expanding device of the air-condition heat exchanger can effectively improve the current situation of smashing or grinding the part of the teeth shapes on the top end of the screw thread teeth inside the air-condition heat exchanger, improve the production quality of the air-condition heat exchanger and improve the EER/COP of the air-condition system.