Based on the practical engineering experiences in LED packaging and design and manufacturing of light source lamps, this book systematically discusses the basic principles and methods of thermal design, and the means to test and evaluate thermal properties; it also introduces a popular simulation software of thermal properties. This book, with the principles and thermal design of LED packaging and light source lamps as a principal axis, integrates the basic technologies of LED packaging and light source lamps, the basic theories of thermal design and simulation tools, and the relevant knowledge about testing and evaluation of LED thermal properties, so that it is able to provides readers with an all-round introduction to the basic principles and practical applications. This book can be used as a textbook or reference book for senior undergraduate students and graduate students of relevant majors, or used as a training material for the practitioners in semiconductor lighting industry and other engineering and technical staff.