Introduction: A broad ligament pregnancy is an extremely rare condition and diagnosis is frequently missed and finally made during laparotomy. This is a case of a young patient with high serum beta-human chorionic gonadotropin (β-hCG) levels after operation because of broad ligament pregnancy. Case Report: A 31-year-old multipara complained of intermittent lower abdominal pain with vaginal bleeding for four months. A color ultrasonography revealed a cystic mass in the left attachment area, indicating an interstitial tubal pregnancy. However, trophoblastic disease could not be excluded. She accepted conservative treatment with methotrexate (MTX) at first, but observation showed that conservative treatment was slow and accompanied with liver function damage. Therefore, exploratory laparotomy was performed. Intraoperative situations and postoperative pathology confirmed broad ligament pregnancy. Her serum β-hCG was sustained at a high level for three months after operation. Her examinations of serum, CT, and ultrasonography could explain this situation. Conclusion: Primary broad ligament pregnancy refers to pregnancy where implantation of the fertilized ovum occurs directly between the two leaves of the broad ligament. The gravid substance was removed, however serum β-hCG could not gradually return to normal levels. This case should be followed-up closely to prevent adverse outcomes.