Abstract： Objective： To observe the clinical effect of Fusu mixture combined with methylprednisolone injection in the treatment of moderate to severe acute respiratory distress syndrome(ARDS) and its effect on blood gas index and inflammatory factors. Methods：A total of 70 cases of patients with moderate to severe ARDS were selected and divided into the observation group and the control group according to the random number table method， 35 cases in each group. The control group was treated with methylprednisolone injection，and the observation group was additionally treated with Fusu mixture based on the treatment of the control group. The clinical effect in the two groups were compared. Before and after treatment，the scores of Murray's Acute Lung Injury Score and Acute Physiology and Chronic Health Evaluation Ⅱ(APACHEⅡ)， the blood gas indexes and the levels of inflammatory factors in serum in the two groups were compared. The adverse reactions in the two groups were compared. Results：The total effective rate was 88.57% in the observation group，higher than that of 65.71% in the control group(P＜0.05). After treatment，the scores of Murray and APACHEⅡ in the two groups were decreased when compared with those before treatment(P＜0.05)， and the scores of Murray and APACHE Ⅱ in the observation group were lower than those in the control group(P＜0.05). After treatment， the levels of partial pressure of oxygen(PaO2)，oxygen saturation(SaO2) and oxygenation index(PaO2/FiO2) in the two groups were increased when compared with those before treatment(P＜0.05)，and the levels of interleukin-1β(IL-1β)，interleukin-10(IL-10) and interleukin-6(IL-6) in serum in the two groups were decreased(P＜0.05)；the levels of PaO2，SaO2 and PaO2/FiO2 in the observation group were higher than those in the control group(P＜0.05)，and the levels of IL-1β，IL-10 and IL-6 in serum were lower than those in the control group(P＜0.05). During treatment， there was no severe adverse reaction related to drugs. Conclusion： Fusu mixture combined with methylprednisolone injection for moderate to severe ARDS patients can effectively improve their clinical symptoms and blood gas indexes，and relieve inflammatory responses in the body with good safety.