BackgroundPulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD). However, it is unknown whether the ratio of forced vital capacity (FVC) to diffusing lung capacity for carbon monoxide (DLCO) can identify PH in the patients with COPD and predict its prognosis.MethodsThe study population I included 937 COPD patients who were admitted to inpatient treatments from 2010 to 2017, and finally 750 patients were available to follow-up the 5-year all-cause mortality (study population II). Clinical characteristics of the study population were recorded.ResultsCOPD patients with PH had a higher FVC/DLCOvalue compared with the patients without PH. The threshold for FVC/DLCOto identify PH in COPD patients was 0.44 l/mmol/min/kPa. Multivariate logistic regression analysis showed that FVC/DLCOwas a significant predictor for PH in the patients with COPD. The study population II showed that the 5-year all-cause mortality of COPD patients was significantly higher in combined with PH group than without PH group. Compared with the survivor group, FVC/DLCOvalue was significantly increased in non-survivor group. The threshold for FVC/DLCOto predict 5-year all-cause mortality was 0.41 l/mmol/min/kPa. Kaplan–Meier survival curves showed that 5-year cumulative survival rate for COPD patients were significantly decreased when the value of FVC/DLCOwas ≥ 0.41 l/mmol/min/kPa. Multivariate cox regression analysis showed that FVC/DLCOwas an independent prognostic factor for 5-year all-cause mortality in COPD patients.ConclusionFVC/DLCOcould identify PH in the patients with COPD and was an independent predictor for 5-year all-cause mortality of COPD.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40001-023-01130-6.