To clarify the effect of Dendrobium devonianum pulp (DP) on relieving constipation, the study evaluated the effect of DP on defecation function, colonic histomorphology, gastrointestinal regulatory peptides, gut microbiota composition, and short-chain fatty acid (SCFA) levels in a mouse model of slow-transit constipation induced by loperamide (LOP). The results showed that compared with the constipation group, DP intervention significantly promoted defecation in constipated mice, reducing the time to the first red fecal pellet discharge by 43.52% (P < 0.05). Additionally, it increased the number of fecal pellets, fecal water content, and colonic transit rate within 5 hours by 113.3%, 27.80%, and 193.33%, respectively, while improving fecal morphology. Histopathological analysis revealed that DP effectively alleviated constipation-induced damage to the colonic mucosal epithelium, restored villi morphology, and increased the number of goblet cells. Biochemical analysis showed that DP significantly increased the levels of excitatory gastrointestinal peptides and decreased the levels of inhibitory gastrointestinal peptides in both the serum and colon of constipated mice. Specifically, following DP intervention, the serum levels of motilin (MTL) and 5-hydroxytryptamine (5-HT) increased to 150.94% and 201.67% (P < 0.05) of the LOP group, respectively, while that of vasoactive intestinal peptide (VIP) decreased by 75.90% (P < 0.05). The colonic levels of MTL and 5-HT increased to 679.60% and 2261.09% (P < 0.05) of the LOP group, respectively, while that of VIP reduced by 59.61% (P < 0.05). 16S rRNA gene sequencing demonstrated that DP increased the Chao1, Shannon, and Simpson indices of the gut microbiota, elevated the Firmicutes/Bacteroidetes ratio, promoted the proliferation of Lactobacillus, and suppressed that of Lachnospira. Furthermore, DP significantly enhanced the levels of propionic and butyric acids in the feces of constipated mice. In conclusion, DP alleviates constipation through multiple mechanisms, including enhancing intestinal motility, repairing colonic tissue damage, balancing neuropeptide levels, optimizing gut microbiota structure, and promoting SCFA production. This study provides a scientific basis for the use of DP as a functional food for improving intestinal health and offers new insights into the application of natural products in gut function regulation.