OBJECTIVE To evaluate the impact of nasal function after Draf III frontal sinus surgery (Draf III) or the modified endoscopic Lothrop procedure (EMLP). METHODS It was a prospective study with self-control. The pre-operative clinical data of 30 patients (from 2010 to 2013, Beijing Tongren Hospital) who underwent Draf III surgery, with the testing results of T&T olfactory testing, acoustic rhinometry and rhinomanometry before and 1 year after operation in these patients were collected in this study. All patients complete visual analogue scale (VAS), a telephone follow-up questionnaire of olfactory function used by Wormald and Lund-Kenndy endoscopy score simultaneously with testings above. Most of 30 patients were chronic rhinosinusitis (CRS) with recurrent nasal polyps or systemic risk factors like asthma and aspirin-intolerance, called refractory rhinosinusitis. SPSS 19.0 software was used to analyze the data. RESULTS 89.3% (25/28) of these patients improved in nasal obstruction 1 year after operation, and the cure rats was 57.1% (16/28, VAS = 0). The level of improvement in nasal obstruction was significantly correlated with pre-operative nasal obstruction severity (r = 0.909, P < 0.01). 76.7% (23/30) improved in olfactory function 1 year after operation in all 30 patients, and 88.2% improved in patients with nasal polyps (CRSwNP). It was also found that olfactory function 1 year after operation was significantly related to Lund-Kennedy endoscopy scores (r = 0.671, P < 0.01), but was not correlated with VAS scores of nasal obstruction (P = 0.349). CONCLUSION The Draf III frontal sinus surgery has a significantly positive effect on olfactory and ventilation function post-operatively, especially on refractory rhinosinusitis.