Objectives: To investigate the alleviating effect of Osmanthus Longjing water extract (OLJ) on ulcerative colitis (UC) mice through the MAPK inflammatory pathway based on network pharmacology and animal experiments. Methods: The common targets and genes of UC and OLJ were collected by network pharmacology， and the key signalling pathways were analysed and selected before experimental validation. In the animal experiment， 24 C57BL/6 male mice were selected and given OLJ (300 mg/kg) by gavage for 4 weeks， and then 3.0% dextran sulfate sodium (DSS) solution was used to drink for 7 days to establish UC model. Recordings were made to analyse the body mass， disease activity index (DAI)， pathological sections of colon tissue， immunohistochemistry， serum inflammatory factor content， MAPK signalling pathway of colon tissue and structural changes of intestinal flora in experimental mice. Results: Network pharmacology results showed that 66 intersection targets of UC and OLJ were obtained， of which the top five core targets were TNF， EGFR， MAPK3， MAPK1， PTGS2. KEGG pathway enrichment analysis revealed that OLJ might act mainly through AGE-RAGE signalling pathway， MAPK signalling pathway and so on. Animal experiments showed that， compared with the model group， the body mass of mice in the GUI increased by 7%， the DAI score was 8.2， and the content of serum inflammatory factors (IL-6， IL-1β， TNF-α) decreased， while the content of anti-inflammatory factor (IL-10) increased (P＜0.05). In addition， after intevention by OLJ， the transcription and protein expression of MAPK signalling pathway genes in colon tissues significantly reduced (P<0.05)； and 16S rDNA analysis revealed that OLJ effectively delayed the relative abundance of Spirochaetota and Escherichia_Shigella induced by DSS. Conclusions: The network pharmacological analysis and experimental validation demonstrated that the extract of Osmanthus Longjing interfered with the MAPK pathway and improved the inflammatory symptoms of DSS-induced ulcerative colitis in mice.