Abstract: Misuse of antibiotics leads to enhanced antimicrobial resistance, disruption of gut microbiota balance, and subsequent gastrointestinal disorders including constipation. Thus, safe and sustainable dietary intervention strategies have gained significant attention. In order to explore the improving effects of Perinereis aibuhitensis powder (PAP) on intestinal function in constipated mice (Mus musculus) and elucidate its underlying mechanisms, we established a constipation model in mice by using a mixed antibiotic solution (Clarithromycin, cefalexin, and amoxicillin), followed by evaluations of small intestinal propulsion rate, time to first black stool defecation, fecal water content, immune organ indexes, inflammatory cytokines, gut microbiota composition, and short-chain fatty acids (SCFAs). Results show that the administration of PAP significantly increased the small intestinal propulsion rate (p<0.000 1), shortened the defecation time (p<0.001), and enhanced the fecal water content in constipated mice (p<0.05). PAP intervention also improved the immune organ indexes (p<0.05), indicating immune homeostasis recovery (p<0.001). Gut microbiota analysis shows that PAP increased the abundance of beneficial bacteria (Such as Bacteroidetes and Firmicutes) and raised SCFAs levels, specifically, acetic acid, propionic acid, and butyric acid increased by 5.7, 61.3, and 11.5 times, respectively, compared with the model group. Additionally, the intervention further alleviated intestinal inflammation (p<0.001). After the intervention with PAP, IL-1β decreased by 35.7% and TNF-α decreased by 30.6%. In conclusion, PAP effectively improves intestinal function in constipated mice. The study provides scientific support for developing PAP-based functional foods for bowel regulation and offers new insights for dietary treatment of constipation.