This book crystallizes the 10-plus years’ research results of senior IoT experts. It analyzes the concept, characteristics and architecture of IoT in simple terms, introduces the key technologies and application scope of IoT at various levels. On this basis, it explores into the IoT-based applications and foresees the research prospect of IoT security. The book is divided into 7 chapters: The first two chapters introduces the concept, characteristics and structure of IoT. Chapter 3, 4 and 5, based on the structure of IoT, respectively discuss the technology system of perception and identification of IoT; network transmission technology system; management service technology system and comprehensive application technology system. Chapter 6 emphatically describes the management service and comprehensive application that are oriented to large-scale application. Based on the overall understanding and technical architecture of IoT, Chapter 7 discusses the security of IoT.