This review systematically summarizes the mechanisms by which gut microbiota acts in CKD-MBD through the "gut-kidney-bone axis": dysbiosis drives chronic low-grade inflammation by impairing the intestinal barrier and promoting endotoxin translocation; alterations in its metabolites (e.g., reduced short-chain fatty acids, accumulation of uremic toxins) and dysregulation of endocrine pathways (e.g., FGF23-Klotho axis, PTH) collectively exacerbate renal injury and abnormal bone metabolism. The gene discussed is PTH; the disease is Marchiafava-Bignami disease.