Objective To investigate the effect of serum exosomes from patients with sepsis on acute lung injury in sepsis rats and its mechanism. Methods Serum samples of sepsis patients were collected. Exo Quick reagent method was used to isolate and purify exosomes from serum samples. The sepsis rat model was established, and the rats were ran domly divided into sham operation group (exposed and turned, cecum only after caesarean section, without any special treatment after operation) , sepsis group (sepsis rat model without any intervention) ? experimental group (serum exo somes from sepsis patients injected by tail vein) and control group (normal saline injected by tail vein), Arterial blood gas analysis, serum inflammatory mediators detection, white blood cell count in bronchoalveolar lavage fluid (BALF) , patho logical observation of lung tissue and detection of wet/dry mass (W/D) ratio of lung tissue were performed in rats of each group. Results Compared with sham operated group, the PH value and PaO2 in sepsis group and control group were sig nificantly lower than those in sham operated group ? while PaCC)2 was significantly higher than those in sham operated group. PaC)2 in experimental group was lower than that in sepsis group, while PaCC)2 was higher than that in sepsis group (P<0. 05). Compared with sham operated group, serum levels of TNF a, IL lg, IL 6 and IL 10 in sepsis group and control group were significantly higher than those in sham operated group. The serum levels of TNF a, IL 1 beta, IL 6 and IL 10 in experimental group were higher than those in sepsis group (P<0. 05 ), The number of white blood cells in BALF of sepsis group and control group was significantly higher than that of sham operated group, while the number of white blood cells in BALF of experimental group was higher than that of sepsis group (P<0. 05), The W/D ratio and pathological score of the lung tissue in the sepsis group and the control group were significantly higher than those in the sham group ’ while the W/D ratio and pathological score of the experimental group were higher than those in the sepsisgroup（P<0. 05）, Conclusion Exosomes in serum of sepsis patients could further aggravate acute lung injury in septic rats ? which might be related to the aggravation of pulmonary inflammatory response by Exosomes.