In recent years,the use of bioprosthetic mitral valves has been increasing,leading to a growing number of patients experiencing bioprosthesis degeneration,significantly impacting their quality of life.The high risk of reoperation has deprived many patients with mitral bioprosthesis degeneration of the opportunity for a second surgery.With the rapid development of interventional procedures in our country,transcatheter mitral valve-in-valve replacement is gradually being accepted by a large number of patients with bioprosthesis degeneration.We report a case of transcatheter mitral valve-in-valve replacement via transseptal puncture.The surgical plan was carefully formulated based on preoperative CT evaluation,and the patient underwent the procedure smoothly with no significant adverse events postoperatively.Transcatheter mitral valve-in-valve replacement may be a better alternative for patients at high risk of mitral bioprosthesis degeneration.