Abstract: OBJECTIVE To observe the clinical characteristics of the children with respiratory syncytial virus (RSV) infection and analyze the association of peripheral blood suppressor of cytokine signaling 1 (SOCS1) mRNA， high-mobility group protein B1 (HMGB1) mRNA with severity of the infection. METHODS A total of 329 children with acute respiratory tract infections who were treated in Huaihe Hospital of Henan University from Mar. 2022 to Mar. 2024 were recruited as the research subjects and were divided into the RS infection group with 88 cases and the non-RSV infection group based on the etiological test. The children of the infection group were divided into the mild group with 56 cases and the severe group with 32 cases according to the severity of disease. The clinical characteristics were compared between the two groups. The expression levels of SOCS1 mRNA and HMGB1 mRNA in peripheral blood mononuclear cells (PBMCs)， the levels of serum interleukin-8 (IL-8)， tumor necrosis factor(TNF)-α， interferon(IFN)-α， the sputum neutrophils and lymphocyte percentage were detected. The association with the severity of RSV infection was observed. RESULTS The incidence rates of wheezing， shortness of breath， fever， vomiting and diarrhea were higher in the RSV infection group than in the non-RSV infection group; the incidence rates of scattered patchy shadow and increased texture on the chest CT imaging were higher in the RSV infection group than in the non-RSV infection group; the expression levels of SOCS1 mRNA， HMGB1 mRNA， the levels of serum inflammatory factors and the percentage of neutrophils in sputum were higher in the RSV infection group than in the non-RSV infection group; while the percentage of sputum lymphocyte of the RSV infection group was lower than that of the non-RSV infection group(P＜0.05). The incidence rates of wheezing， vomiting and diarrhea of the severe group were higher than those of the mild group; the incidence rates of scattered patchy shadow and increased texture on the chest CT imaging were higher in the severe group than in the mild group; the expression levels of SOCS1 mRNA and HMGB1 mRNA of the severe group were higher than those of the mild group(P＜0.05). The expression levels of SOCS1 and HMGB1 mRNA were positively correlated with the levels of serum inflammatory factors， sputum neutrophil percentage， and severity of RSV infection， while they were negatively correlated with the sputum lymphocyte percentage (P＜0.05). CONCLUSIONS The more severe the RSV infection， the more significant the clinical and imaging findings of the children are. The expression levels of SOCS1 and HMGB1 in PMBCs are associated with the serum inflammatory factors， sputum immune cell counts， and the severity of infection.