An implant structure is provided. The implant structure includes an implant body and a screw portion. The screw portion is coupled to a second surface of the implant body such that the implant structure can be implanted into an injured bone via the screw portion. Thus, the implant body partially replaces and thereby repairs the injured bone. Threads of the screw portion have at least a barb unit for preventing the implant structure from rotating in the loosening direction of the screw portion. The at least a barb unit also prevents the implant structure from loosening and displacement so that the service life of the implant structure can be extended.