Objective To explore the effect of different oxygen therapy on chronic obstructive pulmonary disease(COPD) complicated with pulmonary heart disease.Methods A total of 90 patients with COPD complicated with pulmonary heart disease admitted to Yichun People′s Hospital from January 2019 to June 2020 were selected as the research subjects and divided into group A (30 cases), group B (30 cases) and group C (30 cases) according to random drawing method.Group A was treated with Venturi mask ways of oxygen inhalation, group B was treated with continuous positive airway pressure (CPAP), group C was treated with humidified high flow nasal cannual (HHFNC).The breathing rate, heart rate and SpO2, PaO2, PaCO2, pH value of each time after oxygen therapy in three groups were compared, and the hospitalization time, re-intubation rate and patient comfort degree in three groups were analyzed.Results The heart rates of 2, 6, 12, 24, 48 hours after oxygen therapy in group B were higher than those in group A and group C, the differences were statistically significant (P＜0.05).The breathing rates of 2, 6, 12, 24, 48 hours after oxygen therapy in group B were higher than those in group A and group C, the differences were statistically significant (P＜0.05).The PaO2 of 12 hours after oxygen therapy in group B was higher than that in group A and group C, the differences were statistically significant (P＜0.05).The PaO2 of 24, 48 hours after oxygen therapy in group A was lower than that in group B and group C, the differences were statistically significant (P＜0.05).The PaCO2 of 12, 24, 48 hours after oxygen therapy in group A was higher than that in group B, the PaCO2 of 48 hours after oxygen therapy in group A was higher than that in group C, the differences were statistically significant (P＜0.05).There was no significant difference in SpO2 among the three groups (P＞0.05).There was no significant difference in the pH value among the three groups (P＞0.05).The hospitalization time of group A was longer than that of group B and group C, the differences were statistically significant (P＜0.05).The re-intubation rate of group A was higher than that of group B and group C, the differences were statistically significant (P＜0.05).The patient comfort degree of group C was better than that of group A and group B, the differences were statistically significant (P＜0.05).Conclusion HHFNC could effectively alleviate the clinical symptoms of patients with COPD complicated with pulmonary heart disease, improve the ventilation status, reduce the re-intubation rate, improve the comfort degree of patients and shorten the length of hospitalization time.HHFNC is more popular with patients, it is worthy of promotion and application.