Hysteroscopic myomectomy is the first-line treatment for the removal of submucosal myoma in women facing fertility requirements. However, in the face of large diameter type 2 submucosal myoma, patients are at greater risk of complications such as uterine perforation and fluid overload during hysteroscopy. When the diameter of type 2 submucous myoma is greater than 4cm, the three-phase treatment of high intensity focused ultrasound (HIFU), drugs and hysteroscopy is effective and safe. We shared a case of a 30-year-old non-pregnant woman, who had a history of uterine submucous myoma for more than 4 years with symptoms of heavy menstruation, prolonged menstruation and secondary severe anemia. The patient's initial pelvic magnetic resonance results suggested a type 2 uterine submucous myoma with a diameter of more than 4cm. We first performed HIFU on the patient, followed by the patient's oral intake of mifepristone tablets for 3 months, and prior to hysteroscopic surgery, the patient's fibroid type was shifted to type 0, and finally successfully completed hysteroscopic myomectomy (HM). Finally, we conclude that when the diameter of type 2 submucosal myoma exceeds 4 cm, preoperative application of HIFU combined with drug treatment should be considered to maximize the reduction of fibroids, improve symptoms such as anemia and dysmenorrhea, reduce the time required for hysteroscopic surgery, and improve the safety of surgery.