The aim of this study is to explore the operative method, indication and clinical effect of enlarging anterior lacrimal Fossa via Piriform foramen for complex lesions of maxillary Sinus. By imaging and pathology, twenty-one patients with tumors and bone cysts were confirmed that the lesion base was located in the anterior wall of maxillary sinus, alveolar recess and zygomatic recessor even more broadly. All patients were treated with pyriform aperture extend prelacimal recess approach surgery, and followed up for average 25 months. All the 21 operations went smoothly, including 11 cases diagnosed with papilloma, 4 cases diagnosed with maxillary sinus carcinoma, 1 case diagnosed with moderate dysplasia, 1 case diagnosed with fibroangioma, 1 case diagnosed with schwannomas, 1 case diagnosed with maxillary sinus osteoma, 1 case diagnosed with maxillary sinus bone cyst and 1 case diagnosed with dentigerous cyst. Pyriform aperture extend prelacimal recess approach can thoroughly deal with lesions located in each part of the maxillary sinus. Intraoperative blood loss（191.6±44.7） mL. After operations, 6 patients had mild facial swelling, and 8 cases experienced facial numbness; There were no facial scar, collapse and deformation, anterior nares narrowing, tears overflow and other complications. None of the patients relapsed. The enlarged anterior lacrimal fossa via piriform aperture can provide enough space for complete resection of the complex lesions of maxillary Sinus, which are located in anterior wall, Alveolar recess, zygomatic recess and various parts of the base, the postoperative reaction is light, the complication is few.Copyright© by the Editorial Department of Journal of Clinical Otorhinolaryngology Head and Neck Surgery.