Steatocystoma is a benign cyst. It usually occurs in the skin of face, scalp, and neck. We presented a case with a huge cyst in the mandible and the pathological diagnosis was steatocystoma. The surgical treatment of the cyst was done transorally. Aftere removing the cyst by drilling the anterior border of the mandible, we filled the open cavity with gelfoam mixed with antibiotics and then sutured the oral mucosa. The cavity was ossified completely after one and half year. This method is simple andcosts less in comparsion with bone graft and bone dust. The result is good if the oral wound is carefully treated. It is a god option for the treatment of mandibular cyst.