This book systematically discusses Case Based Reasoning (CBR) in the views of theories, methods, and related problems and experiences. The book can be used as a reference in actual applications, in which the research of a few scholars and engineers in the field are introduced. The book is divided into nine different chapters, mainly discussed in the following three aspects: 1) Advances and developments in strategies and specific areas of CBR theory, such as the research of semantic similarity, are introduced in Chapters One, Two and Three in detail; 2) Related research achievements of the applications of CBR in power system analysis, operation and control. These applications include small signal stability early warning, multiple power disturbance recognition, transient stability assessment, fault diagnosis expert system of power transformer, and fault diagnosis and reliability prediction of highspeed railway traction power supply system, which are concretely given out in Chapters Four, Five, Six, Seven and Eight; 3) Applications of CBR in other fields, such as food science, automatic control and mechanical industry, are specifically presented in Chapters One, Three and Nine, respectively.