The net ultrafiltration rate (UFnet rate), defined as the rate of net fluid clearance adjusted for the patient′s weight, has been used in continuous renal replacement therapy (CRRT) of patients with acute kidney injury (AKI) and fluid overload (FO) for several years. Current clinical guidelines do not clearly indicate the relationship between UF net and prognostic indicators such as patient mortality. Moreover, the findings on UF net are controversial due to the different primary morbidities and the wide range of disease severity in critically ill patients. Therefore, in this article, the predictive value of UFnet of CRRT on the prognosis of critically ill patients is reviewed