Objective To investigate the role of RhoA/Rho associated kinase-2 (RhoA/ROCK-2) in the development of pulmonary hypertension (PH) in patients with obstructive sleep apnea-hypopnea syndrome (OS-AHS). Methods Thirty patients diagnosed as OSAHS by polysomnograshy(PSG) test in our sleep laberatoty were recruited as the observation group, and fifteen healthy subjects matched in gender, age and body mass index (BMI) were recruited as the controls. Pulmonary arterial pressure was measured by echocardiography. Serum RhoA/ROCK-2 levels were measured. Results The level of PAP was (47.30±12.85)mm Hg in OSAHA patients complicated with PH, (22.31±3.07)mm Hg in OSAHA patients without PH, which were significantly higher than that in the controls (19.47±1.92) mm Hg (W=175.50, P < 0.05). The serum RhoA and ROCK-2 in OSAHA patients with-out PH (10.43±3.10 and 22.31±16.10 μ/L, respectively) were significantly higher those in the controls (2.94±1.20)μg/L and (6.04±0.28)μg/L, respectively) (W=120.00, W= 121.00, respectively, P<0.05), whereas significantly lower than that in OSAHA patients complicated with PH(14.85±8.49)μg/L, (36.81±12.69) μg/L, respectively) (H =29.172, H =30.242, respectively, P <0.05). There was a positive correlation between PAP and AHI in patients with OSAHS, whether complicated with PH or not(r_s=0.793, r_s=0.887,P <0.05), and there was a negative correlation between PAP and LSaO2 in patients with OSAHS (r_s=-0. 562,r_s = -0.751, P <0.05). There were positive correlations between the level of RboA/ROCK-2 and PAP in patients with OSAHS(r_s = 0.793,r_s = 0.887,P < 0.05). Finally, there was a positive correlation between the level of RhoA and ROCK-2 in patients with OSAHS (r_s = 1.000,r_s = 1.000,P < 0.05). Conclusions OSAHS is an inde-pendent risk factor for pulmonary hypertension. The levels of serum RhoA/ROCK-2 in OSAHS patients with PH were increased in the development of the disease. It may play an important role in the process of pulmonary hyper-tension in patients with OSAHS.