Abstract: Non‑alcoholic fatty liver disease (NAFLD), as a metabolic disease, has shown a constant upward trend in prevalence among the people in recent years. In addition to changing lifestyles and conventional drug treatment, bariatric surgery, represented by Roux‑en‑Y gastric bypass surgery and sleeve gastrectomy, has gradually become one of the treatment options for NAFLD. However, the mechanism of bariatric surgery in treating NAFLD remains to be studied. The "multiple-hit theory", which has gradually been recognized in recent years, believes that NAFLD is formed by the combined effect of multiple mechanisms such as insulin resistance, bile acid metabolism pathway, and intestinal flora. Based on relevant literatures and clinical practices, the authors explore the relevant mechanisms of bariatric surgery for direct or indirect treatment of NAFLD.