In this monograph, the graphene-based field-effect transistor (FET) biosensors are shown to be an emerging sensing platform. Divided into two parts the first set of chapters are devoted to basic knowledge of graphene, graphene FET and its biosensing. In the second part of this book the applications of graphene FET biosensors combined with various biotechnologies are presented. As well as discussing the existing technologies the authors also introduce their own ideas and concepts. Finally the remaining problems in graphene FET biosensors are discussed, along with proposed solutions and prospects for future applications. This monograph allows readers to grasp the basic knowledge and future direction of graphene-based FET biosensors.