To investigate the molecular mechanism of modified Yigong powder(MYG)in the treat-ment of spleen deficiency syndrome based on network pharmacology and analyzed the effect of MYG on gastrointestinal simulated intestinal flora of spleen deficiency dogs and mucosal barrier of Caco-2 cells,as well as the interaction between intestinal flora and mucosal barrier.The molecular mechanism of MYG in the treatment of spleen deficiency syndrome was predicted by network pharmacology.The fecal samples of three canines(12±1)years old with spleen deficiency were collected to establish an in vitro gastrointestinal simulation system,which was divided into the o-riginal fecal sample group,the gastrointestinal simulation group and the gastrointestinal simulation treated by MYG group.The structural changes of the flora in each group were detected by 16S rD-NA sequencing.The metabolites were extracted from the gastrointestinal simulation system trea-ted by MYG group to study its effect on LPS-induced Caco-2 cell mucosal barrier injury model.The cell experiments included the blank control group,LPS model group,modified Yigong metabolite group.The permeability of mucosal was determined by fluorescein sodium,and then relative ex-pression levels of Claudin-1,Occludin and ZO-1 mRNA were determined by qPCR.The correlation between intestinal flora and Caco-2 cell mucosal barrier index after MYG intervention was further analyzed.The results showed that MYG had 76 active ingredients and 45 potential targets for the treatment of spleen deficiency syndrome.Forty key targets were obtained through protein interac-tion analysis,34 items were obtained by GO enrichment analysis,and 16 pathways were obtained by KEGG enrichment analysis.In the gastrointestinal simulation system,compared with the gas-trointestinal simulation group,at the phylum level,the abundance of Firmicutes,Bacteroides and Actinobacteriota increased significantly(P＜0.05),and the abundance of Proteobacteria decreased significantly(P＜0.05).At the genus level,the abundance of Fusobacterium,[Ruminococcus]gna-vus group and Blautia increased significantly(P＜0.05),while the abundance of Escherichia-Shi-gella and Citrobacter decreased significantly(P＜0.05).The diversity index of intestinal flora in the gastrointestinal simulation treated by MYG group was significantly increased(P＜0.05).In cell experiments,compared with the LPS model group,the mucosal permeability of Caco-2 cells in the modified Yigong metabolite group was significantly reduced(P＜0.01),and the expression levels of Claudin-1,Occludin and ZO-1 mRNA were significantly increased(P＜0.01).Correlation analysis showed that there was a certain correlation between bacterial community structure and mucosal barrier indexes.In summary,MYG may act on 40 key targets such as TNF,IL6,IL18,CX-CL8 and AKT1 through 76 active ingredients such as quercetin,arachidonic acid and naringin,and treat spleen deficiency syndrome in dogs through 16 signaling pathways such as AGE-RAGE,FoxO and HIF-l.In addition,the gastrointestinal metabolites of MYG up-regulate tight junction protein mRNA expression,reduce mucosal permeability,and repair mucosal barrier,which may be related to MYG's regulation of flora structure.