The LPS-induced ALI mouse model had a classical pulmonary inflammatory state of the lungs between 48 h and 120 h, but after the administration of UC-MSCs, a decreased lung pathological lesion and inflammatory response was observed at 72 h after UC-MSCs injection, including the lung MPO activity, total protein concentration, lung neutrophil infiltration intensity, the expression of various pro-inflammation cytokines in BALF and the immune response of LPS-induced ALI mice. The gene discussed is MPO; the disease is acute respiratory distress syndrome.