A coil winder for a motor rotor. The winder comprises a frame (1) and a winding component (2) provided on the frame (1). A wire feeding component is provided on one side of the winding component (2). The wire feeding component comprises a servo motor, and an upper roller (7) and a lower roller (8) oppositely arranged and cooperating with each other. The servo motor is connected to the upper roller (7) and lower roller (8) via a belt. A detection component configured to detect a surface defect of an enameled wire is further provided on the frame (1), and comprises an electrically conductive clip holding an end portion of the enameled wire. The detection component further comprises two electrically conductive rings (4) spaced apart and connected in parallel. The electrically conductive rings (4) are connected to the frame (1) via an insulating support frame (6). The electrically conductive rings (4) have an open slot (41), and are provided with a conductive brush (5) on the inner side of the ring. The conductive brush (5) and the electrically conductive clip are connected with a direct current power supply and an alarm. The coil winder can prevent a defective enameled wire from being fed into the winding component, thus eliminating motor failures caused thereby, and providing a high product pass rate.