Abstract: Objective To investigate the effects of allergic rhinitis (AR) on obstructive sleep apnea hypopnea syndrome (OSAHS)in adult. Methods One hundred and twenty adult patients (> 18 years) with allergic rhinitis and OSAHS were selected. Serum IgE, allergen detection, nasal endoscope, and multi-guided sleep monitoring (PSG) were performed. The anti-allergy treatment of all patients, sleeping parameters including apnea hypopnea index (AHI), snoring index, lowest oxygen saturation (LSaO₂) and epworth sleepiness scale (ESS) were compared. Results Compared with pre-treatment, the AHI, LSaO₂, ESS and snore index of patients with persistent AR and mild OSAHS after treatment improved significantly (7.74±0.62)/h vs (10.68±0.94)/h, (89.00 ±0.71)%vs (81.10±0.46)%, (6.80±0.59) vs (8.82±0.66), (97.47±13.64) vs (131.48±19.23), P< 0.05. Compared with pre-treatment, the AHI, LSaO₂, ESS and snore index of patients with persistent AR and moderate OSAHS after treatment improved significantly(15.53±1.83)/h vs (21.73±2.78)/h, (79.00±1.65)% vs (70.60±1.77)%, (9.26±0.39) vs (13.53±1.78), (187.42±28.26) vs(234.39±33.79), P< 0.05. After treatment, ESS and snoring index of patients with persistent AR and severe OSAHS decreased significantly (20.29±1.57) vs (14.47±1.04), P=0.037; (367.96±47.25) vs (252.54±36.47), P=0.029. Conclusion The nasal symptoms improve significantly after regular anti allergy treatment. AR can increase AHI and affect SaO₂ which will cause daytime sleepiness in patients with OSAHS.