Abstract: Objective：To evaluate the relationship between the relative variability of the platelet count in peripheral blood and the severity and prognosis of sepsis patients. Methods：Clinical data of 102 sepsis patients admitted to the Department of Critical Care Medicine (ICU), Zhongshan Hospital, Fudan University from March 2015 to June 2016 were collected. The clinical characteristics of patients with high and low platelet relative variability were compared. The relationship between the relative variability of blood platelet count and the severity of disease and mortality were analyzed. Results：The relative variability of the platelet count was negatively associated with the SOFA (Spearman r=-0.317, P=0.001) and APACHE Ⅱ (Spearman r=-0.397, P＜0.001) scores upon admission into ICU. Multivariate regression analysis showed that the relative variability of platelet count was an independent predictor of ICU mortality in sepsis patients (OR=0.174, 95% CI 0.040~0.758, P=0.02). Conclusions：The relative variability of platelet count in sepsis patients can reflect the severity of the disease and predict the ICU mortality of these patients.