This book systematically discusses the principles, design, interference and testing technology of electromagnetic environment and electromagnetic compatibility. The book is divided into 9 chapters. Chapter 1 elaborates on the basic concept of electromagnetic compatibility and commonly used measurement units and test data processing methods. Chapter 2 introduces the basic knowledge of signal spectrum. Chapter 3 introduces the electromagnetic wave radiation mechanism in electromagnetic compatibility. Chapter 4 introduces the transmission line theory commonly used in electromagnetic compatibility analysis. Chapter 5 and Chapter 6 respectively introduce the conductive emission and immunity, radiated emission and immunity. Chapter 7 introduces the electromagnetic compatibility testing technology. Chapter 8 introduces the electromagnetic interference suppression technology. Chapter 9 introduces the electromagnetic compatibility design method taking the electromagnetic compatibility design of PCB board as an example. This book is suitable for undergraduate and postgraduate students majoring in electronic communication in colleges and universities, and can also serve as reference book for engineers and technicians engaged in electronic system design.