Objective To explore the value of pulmonary ultrasound in the evaluation of pulmonary edema and the guidance of pulmonary therapy in patients with acute respiratory distress syndrome (ARDS). Methods Sixty patients with ARDS admitted to the Department of Critical Medicine of Shanghai Seventh People’s Hospital were randomly divided into a lung ultrasound group and a control group, with 30 patients in each group. The gender, age and etiology of patients were collected, and the relevant data were recorded at the time of admission and on the 7th day, including Acute Physiology and Chronic Health Evaluation Ⅱ (APACHEⅡ) score, Sequential Organ Failure Assessment score (SOFA), white blood cell count (WBC), C-reactive protein (CRP), procalcitonin (PCT), extravascular pulmonary water index, oxygenation index, and mechanical ventilation treatment time. Pulmonary ultrasound score was collected in the pulmonary ultrasound group. The 7-day improvement rate, intensive care unit (ICU) hospitalization time and 28 day mortality rate of the two groups were also collected. The value of pulmonary ultrasound in evaluating the severity, treatment process and prognosis of patients, and the correlation between pulmonary ultrasound score and extravascular pulmonary water index were studied. Results There was no significant difference in APACHEⅡ score, SOFA score, oxygenation index, extravascular pulmonary water index, WBC, CRP or PCT between the two groups before and after treatment (all P>0.05). After 7 days of treatment, the two groups improved, and the pulmonary ultrasound group improved more significantly with more shorter mechanical ventilation time, higher 7-day improvement rate, shorter ICU hospitalization time, and lower 28-day mortality rate (all P<0.05). The extravascular pulmonary water index was positively correlated with APACHEⅡ score and SOFA score, and negatively correlated with oxygenation index. The pulmonary ultrasound score was positively correlated with APACHEⅡ, and SOFA score and extravascular pulmonary water index, and negatively correlated with oxygenation index. Conclusions Pulmonary ultrasound can effectively evaluate the severity of ARDS patients, guide the individualized treatment, and predict the prognosis. It can be used as a routine monitoring method for patients with ARDS.