Objective To explore the correlation between modified lung ultrasound score (MLUS) and oxygenation index PaO2 / FiO2 by replicating the animal model of acute lung injury induced by hydrochloric acid.Methods Twenty New Zealand male rabbits without obvious abnormalities in pulmonary ultrasound examination were randomly divided into control group (5 rabbits) and model group (15 rabbits). After anesthesia (0 h), blood was collected from the femoral artery for arterial blood gas detection. The acute lung injury model was established by intratracheal instillation of different concentrations of hydrochloric acid and normal saline under the guidance of ultrasound. After the establishment of the model (1H, 2h, 4h, 8h, 12h), the pulmonary ultrasound examination and the arterial blood gas oxygenation index (PaO2 / FiO2) examination were performed. The experimental rabbits were killed after 12h, and the lungs were taken for macroscopic observation, and the pathological HE staining of lung tissue was performed. The correlation between MLUS, PaO2 / FiO2 and pathological damage was analyzed.Results PaO2 / FiO2 of the model rabbits showed a decreasing trend at 1h after the experiment, but the decreasing range was not large. It decreased significantly at 2~4h, and tended to be stable after 8h. At 12h, the PaO2 / FiO2 values of the five model rabbits increased. The modified lung ultrasound score and the lung pathological injury score increased with the increase of different hydrochloric acid concentrations, while PaO2 / FiO2 decreased with the increase of hydrochloric acid concentrations. There was a strong positive correlation between the improved pulmonary ultrasound method and the pathological score, and the correlation coefficient was r = 0.963, P < 0.05. The modified lung ultrasound score was negatively correlated with PaO2 / FiO2 score, with a correlation coefficient r = -0.802, P < 0.05.Conclusion The severity of acute lung injury is related to different doses of hydrochloric acid. The modified lung ultrasound score is positively correlated with the pathological injury score, but negatively correlated with PaO2/FiO2 ,MLUS can be used for the evaluation of acute lung injury.