The aim of this study was to comprehensively analyze the structural characteristics of Ziziphus jujuba dates polysaccharide (ZJP‐I) and its potential activity against colitis in vivo. A series of advanced analytical techniques including ion exchange chromatography, gel column chromatography, infrared spectroscopy (IR), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) were used to characterize the structure of ZJP‐I. The results showed that the molecular weight of ZJP‐I was 2.01×104 Da, and it was mainly composed of sugar residues T‐D‐Galp(1→, →4)‐D‐Glcp(1→, →3,6)‐D‐Glcp(1→ and →6)‐D‐Galp(1→ and →6)‐D‐Manp(1→. To appraise the potential efficacy of ZJP‐I on colitis, in vivo experiments were executed by employing a murine colitis model elicited by DSS. The experimental results showed that ZJP‐I could significantly improve the clinical symptoms of colitis mice, including weight loss and colon shortening. Further analysis showed that ZJP‐I effectively inhibited intestinal inflammation and protected intestinal barrier function by regulating inflammatory cytokine homeostasis, alleviating oxidative stress and restoring secretion of short‐chain fatty acids. These findings provided important theoretical basis and experimental support for the potential application of Ziziphus jujuba dates polysaccharides in functional food and medicine.