Red blood cell distribution width（RDW）is a simple and cheap parameter to reflect the heterogeneity of red blood cell volume in peripheral blood. In recent years，as a new inflammatory marker，or combined with other laboratory indexes，it shows unique advantages in clinical outcome evaluation，diagnosis，treatment and prognosis of various pathological conditions. This article reviews research progress of RDW and its derivatives in the relationship between digestive system inflammation and tumor diseases and their possible pathophysiological mechanisms.