Objective To observe the incidence and clinical feature of sleep-related breathing disorder in patients with idiopathic pulmonary fibrosis (IPF). Methods Thirty-four IPF patients who were measured by polysomnography (PSG) were collected in the Department of Respiration of Tianjin Medical University General Hospital. According to the results of apnea hypoventilation index (AHI), patients were divided into pure IPF group (AHI<5 events/h, n=7) and IPF combined with obstructive sleep apnea hypopnea syndrome (IPF+OSAHS) group (AHI≥5 events/h, n=27). The PSG reports of two groups were analyzed, and the correlation between AHI and pulmonary function and oxygen saturation in sleep and at wake were analyzed. Results (1)Thirty-four IPF patients were all demonstrated sleep disorders, low sleep efficiency, increased proportion of stageⅠand stageⅡand decreased proportion of stageⅢand rapid eye movement (REM). The arousal index and the proportion of stageⅠand stageⅡwere higher in IPF+OSAHS group than those of pure IPF group (P<0.01), while the proportion of stageⅢwas lower in IPF+OSAHS group than that of pure IPF group (P<0.01). There was no significant difference in stage REM between two groups. (2)Twenty-seven patients (79%) combined with OSAHS, among which five subjects (15%) were mild OSAHS with 5 events/h≤AHI<15 events/h, and 22 subjects (65%) were moderate-severe with AHI≥15 events/h. The main type of sleep-disorder breathing was hypoventilation, which mainly happened in stage REM. (3) Thirty-four IPF patients showed sleep hypoxemia, and the oxygen desaturation index (ODI) was higher in IPF-OSAHS group than those of pure IPF group (P<0.05). (4)The AHI was positively correlated with body mass index (r=0.791, P<0.05), and was negatively correlated with forced vital capacity (FVC%pred) (r=-0.574, P<0.05) and forced expiratory volume in 1 second (FEV1%pred) in IPF patients (r=-0.664, P<0.05). The lowest oxygen saturation (LSO2) and mean oxygen saturation (MSO2) in sleep were positively related with oxygen saturation at wake (r=0.421 and r=0.464, P<0.05 respectively). Conclusion The IPF patients show severe sleep disorder and hypoxemia, which can be worsen by OSAHS and produce negative effect on daily life. We should initiate active treatment in patients with sleep-related breathing disorders.