Objective To compare the effect between bilevel positive airway pressure (BiPAP) and routine drugs treatment to patients with obstructive sleep apnea hypopnea syndrome ( OSAHS ) complicated with stroke. Methods Twenty-nine patients with OSAHS complicated with stroke were randomly divided into two groups, 15 cases in the treatment group and 14 cases in the control group. Patients in the treatment group were applied BiPAP and routine drugs including degrading intracranial pressure, promoting blood flow, improving microcirculation. BiPAP were maintained for two months and over 10 hours daily. The control group was executed only routine drugs treatment. Results The difference of apnea hyponea index( AHI) and frequency of below 90% O2 saturation during sleep time between pre-therapy and post treatment was significantly higher in the treatment group(36. 8 ± 10. 7 and 105. 3 ± 17. 9) than in the control group (20. 8 ± 8. 1 and 44. 4 ± 24. 3 ) ( P < 0. 01 ) . The difference of lowest nighttime SaO2 between pre- and post-therapy was significantly higher in the treatment group( - 11. 7 ±8. 1)% than in control group(-2. 0 ± 8. 9) % ( P <0. 01). The difference of neurologic impairment score was significantly higher in the treatment group ( 16. 0 ± 2. 6) than in the control group ( 10. 1 ± 3. 6) ( P < 0. 01 ) . As for whole blood viscosity and red blood cell aggregation index,there was no significant difference between pre- and post-therapy(P> 0. 05). Conclusions BiPAP combined with routine drugs can significantly improve sleep anapnea indexs and neurologic impairment scores in patients with OSAHS complicated with stroke than only drug treatment. Blood rheology's indexs could not obtain amelioration in short period.