Progressive cerebral infarction is a difficult problem in clinical work. In recent years， the cause of the progression of acute cerebral infarction and related laboratory indicators have attracted wide attention. Relative dehydration may increase the risk of neurological deterioration in acute ischemic cerebral infarction. This article reviews the mechanism of relative dehydration and laboratory indicators that can represent relative dehydration to explore the effect of dehydration on progressive cerebral infarction， in order to provide more clinical evidence for the early prediction of progressive cerebral infarction.