Mechanisms and Machine Theory is one of the important technical foundation courses for mechanical students in universities. It covers the basic knowledge needed in analysis and synthesis of commonly-used mechanisms and the dynamics of mechanism systems. This course gives students an elementary ability to design or improve mechanical devices. This course plays an important part in cultivating their creative ability and great attention has been paid to this course in engineering universities. This textbook is written according to The Basic Teaching Requirements for the course of Mechanisms and Machine Theory in Advanced Industrial Colleges drawn up by the National Ministry of Education. It contains the authors results on teaching and scientific research during recent years. It aims at cultivating students basic design ability and creative ability in design. Analytical methods and synthesis of mechanisms are emphasized. This textbook reflects new achievements and developments current in mechanism study. Altogether there are twelve chapters. At the end of most chapters, many thinking problems and exercises are enclosed for benefit of students. This book can be used as a textbook for the undergraduates specializing in machinery in advanced engineering universities. It can also be used as a reference book for related teachers, students and engineering technicians. Mainly Ye Zhonghe and LanZhaohui of Fuzhou University wrote the contents of this book. The contents fulfil the fundamental teaching requirements. Dr. M. R. Smith, of the University of Newcastle upon Tyne in Great Britain, has had over thirty years experience of teaching this subject and has checked and embellished the whole book to ensure the fluency of the language. This textbook is therefore a result of international cooperation.