Background <p>To explore the relationship between gut microbiota disorder and perioperative neurocognitive disorder (PND) and postoperative complications after valve replacement.</p> Methods <p>This prospective cohort study involved the patients above 50 years old undergoing elective heart valve replacement surgery. Postoperatively, the cognitive status on the first day without sedation after extubation was assessed. The microbial composition of the feces discharged for the first time after surgery was analyzed, and clinical symptoms of significant disruption in gastrointestinal microbiome within 7 days postoperatively were recorded. Patients with positive microbial results or clinical symptoms were categorized into the intestinal microbial disruption group, while the rest were the normal group. Subsequent analyses were conducted after propensity score matching for age, education duration, and gender between different microbial groups.</p> Results <p>The final inclusion comprised 194 patients, In the PND group, patients had a significantly higher average age(<i>P</i>=0.002) comprising with normal group. Patients in the gut&#xa0;microbiota disturbance group had a higher average age compared to the normal group (<i>P</i>=0.005), with a significantly increased likelihood of developing PND (<i>P</i>=0.001) and other postoperative&#xa0;complications(<i>P</i>=0.008). After propensity score matching, establishing a matched queue&#xa0;consisting of 74 patient pairs, the incidence of PND in the flora disturbance group was 28.4% (21/74), higher than the normal group’s 13.5% (10/74) (<i>P</i>=0.026).</p> Conclusions <p>The incidence of cognitive dysfunction and gut microbiota disorder after cardiac surgery is high, especially in elderly patients. Gastrointestinal microbiome dysbiosis is significantly associated with PND and other postoperative complications. Gastrointestinal microbiome dysbiosis is a risk factor for both PND and other postoperative complications.</p>