This book mainly introduces basic concepts, symbols, presentation, terms, rules and principles of object-oriented design. The first part (Chapters 1 and 2) of this book introduces the basic concepts and history of object-oriented; the second part (Chapter 3 to 7) makes comprehensive introduction to Unified Modeling Language (UML) which has become the de facto standard describing the symbols of object-oriented design; the third part (Chapter 8 to 14) makes in-depth introduction to the principles of object-oriented design; the last chapter (Chapter 15) analyzes the characteristics of software components, including the advantages and disadvantages. This book is targeted at programmers, designers, system engineers or technical managers who use object-oriented technology, whether he is a beginner or a senior.