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: Introduction,Structural Analysis of Planar Mechanisms, Kinematic Analysis of Mechanism, Planar Linkage Mechanisms,Cam Mechanisms,Gear Mechanisms,Gear Trains,Other Mechanisms in Common Use,Combined Mechanisms,Balancing of Machinery,Motion of Mechanical Systems and Its Regulation,Creative Design of Mechanism Systems.At the end of most chapters,many thinking problems and exercises are enclosed.To help Chinese students to read the text,an English Chinese vocabulary is appended. This book can be used as a textbook for the course of Mechanisms and Machine Theory or that of speciality English for undergraduates specializing in machinery in advanced engineering universities.It can also be used as a reference book for related teachers,students and engineering technicians.