Objective To investigate the clinical characteristics of pulmonary hypertension(PH) in patients with chronic obstructive pulmonary disease (COPD) and study the related risk factors.Methods Patients with stable COPD enrolled in this study,undergoing examinations including full pulmonary function tests (PFT),6-minute walk distance (6MWD),Exercise Oxyhemoglobin,Saint.George's respiratory questionnaire (SGRQ) and transthoracic echocardiography.Pulmonary artery systolic pressure (sPAP) ≥ 36 mmHg(1 mmHg =0.133 kPa) was defined as PH.Results A total of 251 patients were finally evaluable in this study.The frequency of PH was 55.4％ (139/251) in patients with stable COPD.Significant differences were seen between patients with PH and without PH respectively in the following factors (mean P ＜0.05):proportion of age ≥ 60 years (69.8％ vs 57.1％),forced expiratory volume in one second (FEV1)(％ predicted) [(47.5±8.2)％ vs(61.2±10.2)％ and(49.8±7.9)％ vs(66.4±11.3)％],sPAP [(41.9 ± 9.1) mmHg vs (28.2 ± 3.2) mmHg],exercise oxyhemoglobin desaturation [(-5.5 ± 3.2) ％ vs(-2.2 ± 1.2) ％],6MWD [(316.0 ± 55.2) m vs(390.0 ±75.2) m].The following variables were negatively correlated with sPAP:6MWD (r =-0.330,P =0.003),FEV1 (％ predicted) (r =-0.210,P =0.024 and r =-0.130,P =0.012,respectively).The following variables were positively correlated with sPAP:age(r =0.560,P =0.031),exercise oxyhemoglobin desaturation ＞ 3％ (r =0.540,P =0.001).Logistic regression test has showed that age≥ 60 years,exercise oxygen desaturation ＞ 3％,FEV1 (％ predicted) ＜ 50％,6MWD ＜ 350 m were risk factors for PH in COPD.Conclusion The incidence of PH in COPD increases with age,yet the performance of lung function and the activity of endurance decrease in elder patients.Sixty years or older,exercise oxygen desaturation ＞ 3％,FEV1 (％ predicted) ＜ 50％,6MWD ＜ 350 m are risk factors of PH in COPD.Echocardiography or right heart catheterization when needed should be considered to confirm the diagnosis.