Under the guidance of Systemic-Functional Grammar(SFG),cohesion is applied to analyze the selected context.Cohesion plays a great role in organizing a whole context and it can be further divided into grammatical cohesion and lexical cohesion.Main ideas of cohesion are illustrated and made it for application,which employs British children's literature-The Water Babies as the object.The research method adopted here is mainly quantitative.Through analyzing selected sections,it is obvious that cohesion helps readers understand the contexts better.Besides,the use of cohesion makes the context more precise and compact.For context,the role of cohesion is irreplaceable.