Objective To compare the application effects of high-flow nasal cannula oxygen therapy and non-invasive positive pressure ventilation in patients with acute heart failure complicated by type Ⅰ respiratory failure.Methods Clinical data of 92 patients with acute heart failure complicated by type Ⅰ respiratory failure, treated in our hospital from January 2020 to January 2025, were retrospectively collected. According to the treatment methods, the patients were divided into a control group and an observation group. All patients received conventional treatments including vasodilation and diuresis. The control group comprised 48 cases, receiving non-invasive positive pressure ventilation in addition to conventional therapy. The observation group comprised 44 cases, receiving high-flow nasal cannula oxygen therapy in addition to conventional therapy. The vital signs (respiratory rate, heart rate), blood gas indicators (arterial partial pressure of oxygen, blood oxygen saturation, arterial partial pressure of carbon dioxide), cardiac function [left ventricular end-diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), left ventricular end-systolic diameter (LVESD)] and myocardial injury markers [creatine kinase isoenzyme (CK-MB), N-terminal pro-B-type natriuretic peptide (NT-proBNP), cardiac troponin I (cTnⅠ) ] were compared between the two groups before treatment and 24 hours after treatment. The complications such as aspiration, nasal and facial pressure injuries, flatulence, and intolerance were recorded. The tracheal intubation rate, treatment failure rate, and mortality rate at 6 months were compared between the two groups.Results The respiratory rate and heart rate in the observation group were significantly lower than those in the control group after treatment (P < 0.05). Within each group, both the respiratory rate and heart rate decreased significantly after treatment compared with baseline (P < 0.05). In both groups, PaO₂ and SpO₂ increased significantly while PaCO₂ decreased significantly after treatment compared with baseline (P < 0.05). LVEF was higher and LVEDD and LVESD were lower after treatment than those before treatment in both groups (P < 0.05). The levels of CK-MB, NT-pro BNP and cTnⅠ after treatment were also lower relative to pre-treatment values in both groups (P < 0.05). The overall complication rate in the observation group was lower than that in the control group (P < 0.05). There was no difference in the tracheal intubation rate, treatment failure rate, or mortality rate between the groups (P > 0.05).Conclusion High-flow nasal cannula oxygen therapy is superior to non-invasive positive pressure ventilation in improving vital signs and blood gas indicators in patients with acute heart failure complicated by type Ⅰ respiratory failure, with a lower incidence of complications and better safety.