Objective：To evaluate the safety and effectiveness of high intensity focused ultrasound（HIFU） combined with ultrasound-guided curettage for treating type Ⅱ caesarean scar pregnancy（CSP）. Methods：Eighty-two patients with type Ⅱ CSP from Suning Central Hospital were divided into 3 groups based on the diameter of pregnancy sac：10-mm group，20-mm group，30-mm group. All the patients from the three groups were first treated with HIFU，and then had ultrasound-guided curettage. Results：The number of the three groups was 23，36，23 respectively. The sonication power used for the three groups was 397（350 to 399），399（387 to 400），400（399 to 400） W respectively（P=0.000）. The treatment time for the three groups was 37.0（27.0 to 48.0），62.0（37.5 to 78.0），64.0（46.0 to 84.0） min respectively（P=0.001）. The sonication time for the three groups was 250（200 to 321），415（252 to 680），522（400 to 800） s respectively（P=0.000）. The average sonication intensity for the three groups was （435.7±128.0），（487.0±105.1），（558.4±118.9） s/h，respectively（P=0.002）. The median blood loss in the procedure of curettage was 20（10 to 30），20（15 to 35），30（20 to 100） mL respectively（P=0.000）. When treating the bigger size sac，the higher the treatment power and treat－ment intensity，the longer sonication time and treatment time，and more blood loss during curettage was observed（P<0.05）. The median time of human chorionic gonadotropin（β-hCG） level returning to nomal was 25（24 to 31），27（23 to 30），31（24 to 37）d respectively. No statistically significant difference was observed among the three groups（P=0.248）. Conclusion：HIFU combined with ultrasound-guided curettage can be safely used to treat CSP，especially for the sac smaller than 30 mm. For CSP patients with large sac，higher son－ication power and longer sonication time should be given to reduce the blood supply of sac，and therefore to reduce the risk of massive bleeding during curettage.