Background: The endoscopic transnasal approach has been proven to have advantages on the removal of the tumors in pterygopalatine fossa (PPF) and infratemporal fossa (ITF). Herein, this study aimed to describe a modified approach for resection of the tumors in these areas, both in cadaveric specimen and clinical patients. Methods: The 20 adult cadaveric specimens and five patients with tumors in PPF and ITF were enrolled in this study. For the cadaveric specimens, ten were simulated anterior transmaxillary approach and ten were performed modified endoscopic transnasal transmaxillary approach. The exposure areas were compared between two groups and main anatomic structure were measured. Surgery was operated in the five patients with tumors of PPF and ITF to verify the experience from the anatomy. Perioperative management, intraoperative findings and postoperative complications were recorded and analyzed. Results: The modified endoscopic transnasal transmaxillary approach provided as enough surgical exposure and high operability to the PIT and ITF as the anterior transmaxillary approach did. The diameter of maxillary artery in the PPF was 3.77 +/- 0.78 mm (range: 2.06-4.82mm), the diameter of middle meningeal artery in the ITF was 2.79 +/- 0.61 mm (range: 1.54-3.78 mm). Four patients who suffered schwannoma got total removal and one of adenocystic carcinoma got subtotal removal. The main complications were facial numbness and pericoronitis of the wisdom tooth. No permanent complication was found. Conclusions: With the widespread use of neuroendoscopy, the modified endoscopic transnasal transmaxillary approach is feasible and effective for the resection of tumors located in PPE and ITF, which has significant advantages on less trauma and complications to the patients.