Objective To discuss the diagnose and treatment of puerile cases with serious cellulitis of floor of mouth. Methods The data of 12 cases with serious cellulitis of floor of mouth were retrospectively analyzed. Results 12 cases with serious cellulitis of floor of mouth were all cured by systemic anti- infection and topical incision and drainage. Conclusion The key to treat serious cellulitis of floor of mouth is systemic anti- infection and topical incision and drainage.