This is the proceedings of the 6th International Symposium on History of Machines and Mechanisms that was held in Beijing, China, in September 2018.  The Symposium provided an international forum for presenting and discussing historical developments in the field of Machine and Mechanism Science (MMS). Special sections focused on the following topics:.       modern reviews of past works·       engineers in history, and their works·       direct memories of the recent past·       the development of theories·       the history of the design of machines and mechanisms·       development of automation and robots·       the development of teaching of MMS·       the schools and institutes of mechanical engineering·      the heritage of machines and mechanisms