Background: It remains uncertain whether vitD3 supplementation is beneficial for remission of Crohn's disease (CD). The influence of vitD3 supplementation on Infliximab (IFX) efficacy was retrospectively analyzed in Chinese CD patients. Methods: Patients with moderate-to-severe CD, who were bio-naïve and prescribed with IFX treatment for at least 54 weeks were recorded. VitD3 supplementation was defined as patients additionally took oral vitD3 (125 IU/d) within 3 days after the first infusion and persisted in the whole follow-up period. Disease activity was assessed using Harvey-Bradshaw Index (HBI). Serum cytokine profiles were quantitatively analyzed in a subset of all patients at baseline and 54-week after intervention.